S. Nathaniel Adams

Documenting history as well as my experiences with repairing and restoring vintage guitars. Formally known as STL Amateur Luthier

Home Top Ad

 About Andrew Groehsl (b. 1859, d.1952) was an Austrian-born luthier most well known for founding his own instrument company in Chicago whic...


Andrew Groehsl (b. 1859, d.1952) was an Austrian-born luthier most well known for founding his own instrument company in Chicago which later became the Kay Musical Instrument company. He was married in 1893 to Amalie Bohmann (no relation to luthier, Joseph Bohmann) [1]. He was also known in the Chicago area as a "legendary" player of the Tamburitza and I believe there is a passage referencing him in the book Tamburitza America by Milan Opacich [9]

Andrew Groehsl Company

The Andrew Groehsl Company (also called the Groehsl Mandolin Company by some modern authors) was a manufacturer of musical instruments in Chicago during the turn of the 20th century. Andrew brought to America his knowledge of Eastern European instrument construction and built both traditional Serbian and modern American instruments. He also built instruments for Harry J. Flower's music shop under the MayFlower name which I have compiled research about in this article


The company is founded around this time


The factory is listed as being located at 81 Illinois Street and employing four individuals; one under 16 and three above 16 [6].


Andrew is listed as being a musical instrument manufacturer at lives at 3406 Perry [5 p.547]


The company is purchased by Henry "Kay" Kuhrmeyer, Frank C. Voisinet, and Charles G. Stromberg and becomes Stromberg-Voisinet. [2][4]


Andrew is listed as being a musical instrument repairman and lives at 3406 Greenview Ave (perhaps his street changed names?) [5 p.45]


Andrew Groehsl dies at the age of 93. His occupation is listed as being a violin maker. [1].


Andrew Groehsl built a variety of instruments during his lifetime including traditional Serbian instruments and modern American instruments. Of the traditional instruments from his culture, I've seen his builds of a Tamburitza or Tamburica which, to my ignorant eyes, looks like a 5 string guitar with ornate inlays like one would expect on a European bowl back mandolin.

This quote from a September 1979 issue of the Battle Creek Enquirer in Michigan mentions an instrument built by Andrew Groehsl
. . When the music ended, Blazekovich packed away his 50-year-old bugarija, which looks like a five-string guitar. The instrument couldn't be duplicated today, he said. It has a butterfly pattern inlaid into mahogany on the body and bears the name of Andrew Groehsl, who made East European instruments a half-century ago in Chicago. [8]
His instruments can be styled very ornately, especially his European instruments, which has led to a lot of attribution to Washburn and the Larson Brothers but his instruments are entirely his own. 

They are all French polished and are constructed with Brazilian Rosewood or mahogany and Spruce. Some instruments have the Stauffer-style headstocks and they have colorful wood or pearl bindings. 

Groehsl label from a guitar 
Address listed as 755 Perry Street
Image Credit: Reverb - Lazy Angels Music

Groehsl label from a tamburitza 
Address listed as 3406 Greenview Avenue
Image Credit: Private Seller


[1] https://www.familysearch.org/ark:/61903/1:1:Q2M4-J2LL
[2] https://mtr.arcade-museum.com/MTR-1922-74-10/31/
[3] https://www.familysearch.org/ark:/61903/1:1:N7X2-7XC
[4] https://jedistar.com/groehsl/
[5] https://www.chicagoancestors.org/sites/default/files/downloads/1923g.pdf
[6] https://books.google.com/books?id=Kj8oAAAAYAAJ&pg=PA267&dq=Groehsl+company&hl=en&newbks=1&newbks_redir=0&sa=X&ved=2ahUKEwiYtZbSvpnuAhULWs0KHaYyB3Q4ChDoATACegQIBBAC#v=onepage&q=Groehsl%20company&f=false
[7] https://archive.org/details/lakesideannualdi1911unse/page/546/mode/2up?q=groehsl
[8] https://www.newspapers.com/newspage/205755709/
[9] https://babamim.com/milan_opacich_usa_national_treasure

Tony J Placht blue label from a 1940s Regal guitar Anton Joseph Placht was born in 1867 in Germany to luthier Joseph Placht (b.1840, d. 1896...

Tony J Placht blue label from a 1940s Regal guitar

Anton Joseph Placht was born in 1867 in Germany to luthier Joseph Placht (b.1840, d. 1896) and his wife Francisca. He was the third of seven children [1][2].

J. Placht & Son

J. Placht & Son was established by Joseph Placht and sold a variety of band instruments with a smaller line of stringed instruments. It is unclear if Joseph Placht continued to build instruments after moving to the United States. 
  • Shop Located at 113 South Broadway [3]
  • 1896 - Owner and father Joseph Placht passes away
  • 1898 - Currently employed: Frances and Joseph Jr [3]
  • 1908 - Changed names to J. Placht & Bro [5]
  • 1916 - Shop moved to 613 Pine Street [15]
  • 1925 - Opened a branch store at 6311 Delmar Blvd [11]
    • Advertised York band instruments and Washburn stringed instruments
    • Lyon and Healy commended the store's billboard for the Washburn line of instruments as the first "out-of-door" sign for their lines [13][16]

Tony J. Placht

Anton Placht Americanized his name to Anthony and began going by Tony as early as 1897. He lived at 1703 Cora Avenue [3]. He married native Missourian Emelia (or Emillie) Placht (nee Dieckmann) [4]. They had two children, Margariete (b. 1900, d.?) and LeRoy Anthony (b. 1905, d. 1970) [17 p.73]
  • 1897 - Shop opened (approx) at 1002 Olive Street [12]
    • Carried Washburn instruments and sheet music
    • Had been in business with his father for a number of years prior
  • 1908 - Shop moved to 920 Pine Street [6]
  • 1917 - Shop moved to 1001 Pine Street (its final location) [8]
    • The move was influenced by proximity to the "Piano Row" on Pine Street [14]
    • Newspaper advertisements were looking for "secondhand musical instruments" and advertising repair services. 
  • 1940 - Anthony's son LeRoy wrote "manager" of a "retail music store" in his census [18]
  • 1944 - Anthony J Placht dies aged 77 [4]

L. Tony Placht 

The son of Anthony, LeRoy took over the music shop after his father's death in 1944 and ran the store until 1959 when he put out an advertisement looking for work [19]. 

Its tragic as the guitar market was on the edge of another boom with the Beatles and he could've gotten another decade's worth of business. 

Present Day

The Placht family was responsible for distribution of an untold number of instruments to St Louisans and residents of the bi-state area. Their legacy and history deserves to be remembered as instruments bearing their labels can still be found like the Regal guitar I found that led me down this quest. 

Broadway has been extensively redeveloped so Joseph's original building no longer exists. The J. Placht & Bro building on Delmar Boulevard is still standing. Pine Street has also been redeveloped but Tony's location at 1001 Pine still exists and is currently a bank. The building at 1002 Olive Street may also still be standing. Tony's home is still standing, sorta, but it is in a dangerous area of town.


[1] https://www.familysearch.org/ark:/61903/3:1:33S7-9YBV-2CW?i=1&cc=1417683&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3AM6FJ-3CF
[2] http://genealogy.mohistory.org/genealogy/name/88198?a=1
[3] https://www.familysearch.org/ark:/61903/3:1:3Q9M-C37H-6JMX?cc=3754697&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3ADD7N-Y2T2
[4] https://www.findagrave.com/memorial/47760342/tony-j-plach
[5] https://www.newspapers.com/image/138901007/
[6] https://www.newspapers.com/image/138901007/?terms=tony%20anthony%20joseph%20placht&match=1
[7] https://www.newspapers.com/image/572159460/?terms=tony%20placht&match=1
[8] https://www.newspapers.com/image/138256321/?terms=tony%20placht&match=1
[9] https://www.newspapers.com/image/573281652/?terms=tony%20placht&match=1
[10] https://mtr.arcade-museum.com/MTR-1908-47-2/index.php?page_no=38
[11] https://mtr.arcade-museum.com/MTR-1925-81-3/35/
[12] https://mtr.arcade-museum.com/MTR-1897-25-3/21/
[13] https://presto.arcade-museum.com/PRESTO-1925-2019/22/
[14] https://mtr.arcade-museum.com/MTR-1914-59-2/36/
[15] https://mtr.arcade-museum.com/MTR-1916-63-18/37/
[16] https://mtr.arcade-museum.com/MTR-1925-80-10/29/
[17] https://dnr.mo.gov/shpo/survey/SLCAS039-S.pdf
[18] https://www.familysearch.org/ark:/61903/3:1:3QS7-89MB-18QQ?i=14&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3AK74B-663
[19] https://www.newspapers.com/image/570728186/?terms=%22tony%20placht%22&match=1

  Biography Anton Diener (1849-1916) was born to Konrad and Anna Maria Diener (nee Dinz) in Germany and he immigrated to the United States a...



Anton Diener (1849-1916) was born to Konrad and Anna Maria Diener (nee Dinz) in Germany and he immigrated to the United States aboard the Westphalia in 1872. His occupation was listed as a "joiner" [1][2]. He married Anna Maria Westenberger (1852-1905) in 1877 [3].

According to the 1900 census, the earliest available, Anton was listed as a "mfg of instruments" and had a 22 year old son, George, who was listed as an "instrument maker" [4]. In the 1910 census, Anton was living in his son's house, after his wife had passed, and both were listed as "manufacturer" in "own shop". Anton died in 1916 and his final occupation was listed as "music mfg" and the family still resided in their home at 2028 Tremont St or 2028 Fremont St [6][7]. 

George Diener (1878-1951) married Anna Placht, the third Diener to marry a woman named Anna. [7]. In his WWII draft registration card, he was listed as working at his "own business" doing "musical instrument repairing"  [8]. He would continue to list his occupation as a repairman for musical instruments through every census until his death in 1951 [9]. They had two children, Agnes and Edward, who did not take up the family trade and so the line of instruments ended with George.

It is unclear where these instruments are produced and how they were sold as I cannot find a shred of advertising in newspaper scans or any evidence of a business location. It's possible that they were built out of their home. Either way, George did not appear to carry on with building instruments after his father passed so the "A. Diener" guitars are likely the only ones that came from this father-son trade. In the time period that George did his repair work, it was not uncommon for labels to be affixed in instruments after a repair was completed so perhaps there exists "G. Diener" repair labels. I cannot say for sure.


Anton Diener's instruments have a label with his name, "A. Diener", followed by the name "Laclede Guitar" in fancy script, and finally the city "Chicago". All are on separate lines. 


[1] https://www.familysearch.org/ark:/61903/1:1:KD3C-2KW

[2] https://www.familysearch.org/ark:/61903/1:1:QPT8-5PWJ

[3] https://www.familysearch.org/ark:/61903/1:1:D4MJ-1M3Z

[4] https://www.familysearch.org/ark:/61903/3:1:S3HY-DHX3-JBV?i=28&cc=1325221&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3AMSQ3-28T

[5] https://www.familysearch.org/ark:/61903/3:1:33S7-9RVX-ZD?i=21&cc=1727033&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3AMKZF-LGT

[6] https://www.familysearch.org/ark:/61903/1:1:NQ2L-3MK

[7] https://www.familysearch.org/ark:/61903/1:1:H9JG-3NN2

[8] https://www.familysearch.org/ark:/61903/3:1:33S7-814K-SLN?i=1785&cc=1968530&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3A7W3Y-5L3Z

[9] https://www.familysearch.org/ark:/61903/1:1:Q2MH-KPQC

 Repairing Broken Kluson Tuning Machines Today we are fixing one of the most common breaks on a set of 3-on-a-plate Kluson "single line...

 Repairing Broken Kluson Tuning Machines

Today we are fixing one of the most common breaks on a set of 3-on-a-plate Kluson "single line" tuners. The D tuner shaft sustained an impact and the cast brass had sheared. These tuners were designed to remain sealed and so opening them seems daunting but they are quite simple in design 

You can seriously disfigure and even ruin your tuners if done improperly and patience is key to success. If you're unsure, STOP, install a set of replacement Klusons, and keep the originals in the case for a proper repair

This is the wrong (but far too common) approach.
If the tuners were simply removed and replaced then these could've been repaired

Shame because these were a rare set of Safe-Ti-String posts with butterfly buttons

What You'll Need

  • At least one donor Kluson tuning machine from the same era (I have yet to see if the reissues will work)
  • Ball peen or similar small hammer
  • Junky wood chisel
  • Nail punch (a few different sizes wouldn't hurt)
  • Padded bench vise
  • Needle-nose pliers
  • Soldering Iron
  • Thin CA glue with a whip tip

The Process

Using a cheap chrome vanadium chisel, I bend the forward tab upwards where I can use a nail punch and ball peen hammer to carefully bend the tab to a vertical position. Use light taps and try not to lever off the plate! If you stress the tab too much it will snap off and then you're in trouble 

Then tap the tab through the plate and you should be able to carefully bend the casing backwards enough to remove the broken worm gear. 

 Have you ever broken off the tab on a soda can by rocking it back and forth? You don't want that to happen so the fewer times you bend the back tab, the better

Here is the broken brass worm gear and shaft with the replacement I pulled from a 'donor' set of broken Klusons. It doesn't matter if your part comes from the treble or bass side, they will work all the same. I'll use alcohol to clean off the old grease and crud

Seat the replacement worm in the tuner casing and make sure it fits

Now you will gently bend the casing back into place, you may need to bend the front tab so that it is aligned with the hole in the plate.

The plate has become slightly bent, this isn't difficult to fix but I would recommend waiting until the end

Using my padded vise, I compressed on the tuners which seated the casing back into the plate and locked the worm gear in place

Using a nail punch and taking gentle hits, I bend the tabs back into place. If your punch slips you'll scratch the back of the plate which isn't the end of the world but looks cleaner if you avoid it

I'm no machinist so I don't really have a go-to lubricant for these parts (friendly reminder WD-40 is not a good choice) but I use 3-in-one PTFE and it has worked out well for me

Put the broken shaft into your padded vise with gentle pressure and use a soldering iron to apply heat. If you get the shaft too hot, you will melt and distort the button. I typically apply heat for 10-15 seconds, pull on the shaft with needle nose pliers, rinse and repeat until it's free. 

Now the button is free from the broken shaft and we can see two bends which would be consistent with a collision. The tuner button got slightly hotter than desired and the button has formed a small collar of melted material around the hole. I'll use a sharp razor blade to trim it back.

Note that the shaft has a "spear" shape with a "wing" on either side, this cuts into the button and prevents them from spinning freely on the shaft. 

Using your soldering iron again, heat up the worm shaft on your tuners (until the string post is warm) then press the plastic button down on it. Then, acting quickly while everything is warm, put the tuners into a padded vise and push them together. The existing tuner buttons will act as a depth stop so you don't push the button too far.

Important things to note
  • Ensure that the "wings" on the shaft and the button are lined up, we don't need to put any more tension on this old plastic than necessary
  • If the shaft is too cold then you'll see the button distend or see stress cracks forming
  • If the shaft is too hot then you will see it melt and also distend 
  • If your button goes on crooked, heat up the shaft again and you should be able to shift it by hand or by holding it a vise.
I flood the inside of the button with thin CA which reinforces the bond between the melted plastic and the brass and fills any gaps

And here is the finished product! The patina on the replacement brass shaft (top left) doesn't match the existing ones but they are functionally identical and I'd call that a rescued set of tuners!

I don't believe the tuner shafts could be brazed back together and remain strong but I hold onto the old parts anyways. Perhaps replicas could be cast 

Finally, if the plate had become bent from the earlier steps, simply place it in a padded vise and apply light pressure with your hand to coax it back into place. The metal is thin and pliable, so it is not hard to correct

These are rare photos I have located that show the Kay guitar factory in addition to the incredible photos from the 1964 book Kay The Story...

These are rare photos I have located that show the Kay guitar factory in addition to the incredible photos from the 1964 book Kay The Story Of A Guitar

Image Credit: https://www.newspapers.com/image/71789588/?terms=%22kay%2Bmusical%22

Image Credit: https://www.newspapers.com/image/71789588/?terms=%22kay%2Bmusical%22

Kay The Story of a Guitar This is a very rare promotional booklet distributed by the Kay Musical Instrument Company which offers a glimpse i...


The Story of a Guitar

This is a very rare promotional booklet distributed by the Kay Musical Instrument Company which offers a glimpse into the inner workings of the factory and the manufacturing process from raw timber to a finished instrument. 

 Please don't copy or reupload this booklet, thank you :)

 This is a scan from Set 42 of the Howard W. Sams & Co. Photofact series. It includes the schematic as well as a description of the part...

 This is a scan from Set 42 of the Howard W. Sams & Co. Photofact series. It includes the schematic as well as a description of the parts and values that go into making the amplifier. 


About Theodore (Theodor) August Gast was born October of 1874 in Germany and immigrated to the United States. He was married to Martha Schal...


Theodore (Theodor) August Gast was born October of 1874 in Germany and immigrated to the United States. He was married to Martha Schalk in the year 1900 [3]. In the 1910 census he was listed as a worker in a musical instrument factory [4]. By 1917 he was the shop foreman at the Harmony Company [1]. In 1940, he was listed as violin maker for an unnamed musical instrument company [2]. He died in 1955 [5].

Airplane Bridge (1928)

Gast designed the airplane bridge and X bracing that appears on the Harmony Johnny Marvin, Roy Smeck, and similar higher end models from the era. 

Tailpiece Connected To The Back (1931)

This is a unique patent for a tailpiece that connects to the back of the guitar because, as the patent states, the back isn't directly affected by the vibration of the strings compared to the top.


[2] https://www.familysearch.org/ark:/61903/3:1:3QS7-L9MB-JKFH?i=12&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3AK4M8-P2X
[3] https://www.newspapers.com/image/350275873/?terms=%22theodore%2Bgast%22
[4] https://www.familysearch.org/ark:/61903/3:1:33S7-9RV9-H92?i=36&cc=1727033&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3AMK8S-932
[5] https://www.findagrave.com/memorial/184902346/theodore-august-gast

Handel tuners with plain buttons on a pre-1910 Flower & Groeshl "Mayflower" guitar Handel Tuners with inlaid buttons Image Cre...

Handel tuners with
plain buttons on a
pre-1910 Flower
& Groeshl "Mayflower"
Handel Tuners with inlaid buttons
Image Credit: VintageAmericanGuitar.com

Handel (meaning "trade" in German) tuning machines appeared on early Gibson mandolins until about 1918 (when they disappeared) and included pearl and silver wire inlaid into an faux-ivory celluloid button [1]. These tuners also appeared on Vega cylinder-back mandolins and similarly inlaid buttons appeared on some Joseph Bohmann instruments from earlier in the century. The tuning machines with plain buttons also appeared on select other instruments from the era.

These tuning machines are incredibly difficult to find information about and a lot of the information out there relies on circular referencing without any solid paper trail to back any of the sources up. I am seeking to answer a few questions and put together a solid explanation as to the origin of these tuning machines.

Does "Handel" refer to the designer of the buttons or the tuning machines as a whole?

Were Handel tuners actually made in Germany? Who made them?

Why did they disappear from Gibson instruments after 1918?

"Saxony" Theory

This particular origin story comes from a 2003 page by Vince Brennan on the now defunct OldMusicProject.com. It claims that there was a village in Saxony, Germany that was home to the Handelstein family that carved bone buttons by hand up until the Great War took most of their laborers and made it un-American for Gibson to import their materials

The first issue is that these buttons are not bone but are an early plastic made to resemble ivory or bone which would be the first, major, flaw in that theory. Secondly, I realize the limitations of searching for an obscure German village via English Google but even MandolinCafe.com commenters, as far back as 2006, seemed to realize that no references to such a village exist. Now, in 2020, the only references I can find are from commenters on MandolinCafe referring to the tuning machines. Thirdly, the tuning machines disappeared from Gibson instruments in 1918 (the end of WWI) and the war started four years earlier and I doubt Gibson had 4 years worth of buttons lying around. The timeline doesn't seem to make much sense
The tuners alone are worth $250.00 a set.  These were made in Germany in ONE little village in Saxony,  Handelstein.  The industrious Handelsteiners had done inlaying and carving of bone and ivory for at least 200 years,  thus the pegs are commonly referred to as "Handel Tuners" . Christian Martin made sure (another saxon, he) that he imported the ivory and bone tuners from there to fit his more expensive guitars (actual cost 1860 for a CF Martin top-of-the-line parlour guitar? $45.00!)
It was a cottage industry for someone to shape the bone thumb-pegs and then someone else would engrave the bone thumb-pegs and then someone else would inlay the flowers on the bone thumb-pegs  and someone else would..... you get the idea. 

Well,  a complication arose....called WW1.  Being experts in engraving bone, most of Handelstein's young men went and started engraving French and Belgian skulls with lead, and the industry died.  When the US entered the war, it was now un-patriotic to use these and so Gibson sent all it's stock back to the importer and went to plain bone thumb-peg tuners from then on in.  Until then, these Handel tuners were a premium feature on not only mandolins, but guitars, mandolas, mandocellos, etc. 

http://www.oldmusicproject.com/23JAN2003.html [2]

"German Buttons" Theory

This theory originated from the famous Roger Siminoff in a 1981 issue of Frets and comes from a website that cites him. The website notes that after 1918, the buttons switched from the ornate style to a plain "ivory-colored" button and I believe the author also realizes that the buttons are not bone

 The 'Handel' machines featured bone knobs that were fancily inlaid with mother-of-pearl, abalone, and fine wire.... Because the knobs were cemented onto the shafts, they are very difficult to remove; so you have to think of the knobs and their attached gears as a unit.  It was originally believed that the gears and backstraps were made in this country, then sent to Germany for the Handel firm to install the inlaid knobs; but Handel actually did the entire job overseas....  They were quite beautiful, and the workmanship was excellent.


"Handel Lamp Co" Theory

The Handel Company from Connecticut existed from 1885 to 1936 and made glass lamps which are desirable [5]. MandolinCafe users attempted to draw a connection between the two but were unable to definitively say that the company produced such a product [3]. 

"Waverly" Theory

I also stumbled across a few references both on the internet and through communication with other vintage instrument repairman and specialists that attributed the tuning machines to the Waverly company. The Waverly company was established in 1918 which again would be post WWI and after Gibson had ceased to use the buttons. Perhaps Waverly produced copies later on? I do not know but the originals cannot be Waverly-made

"Japanese Buttons" Theory

Paul Hostetter of MandolinCafe.com claimed to have seen a jar of new old stock Handel inlaid buttons by an anonymous New York music dealer. The dealer claimed they came from Japan. This was quickly debunked by user thistle3585 who said that Japan didn't become a big source for celluloid until the 1920s.
An instrument dealer from NYC, whose name shall not be uttered, once showed me a quart jar full of Händel buttons, new-old stock, so to speak - never used - and swore they came from Japan, and were pressed onto gears by various makers in the US. I'm not sure how he knew they were from Japan. This guy also loves to call rosewood Circassian walnut.

[3 p.4]


Louis Handel Company of New York

The Louis Handel Company was founded in 1911 according to New York business records. The company is fairly enigmatic and it was difficult to find references to it until I stumbled upon a case from the 1923 that came before the New York Supreme Court and thus was digitized by Google Books. The case involved some sort of payment dispute and business relation between Louis Handel and Ferdinand Suren (who also founded his own manufacturing company for musical instrument parts). 

I read the entire transcript (so you don't have to) and picked out any important details and mentions of the company's operations. The company was located at No. 138 Centre Street in Manhattan, New York and had been valued at $45,000 in the 1920s so they weren't a small operation. 

Louis (b.1853) was a little more difficult to track down as there were a number of folks sharing his name in New York during that time period including a duck farmer/innkeeper, and a grocer. But I was able to discern through his daughter's name, which appeared in both the court case and his obituary, that he died on July 3rd, 1933 [8]. I am not sure of to what extent the company continued after his death but his daughter, Anna C. Thomas (b.1883, d.1946), held stock in the company during its existence.

The company was involuntarily dissolved in 1985 but I've seen it before where companies are dissolved decades after they ceased to exist. So 1985 is a hard end date but I believe it likely closed down much earlier. Their family line, unfortunately, does not continue to the present day [6]

Transcript from the court case that definitively ties
the Handel company to making "patent heads" (tuning machines)
for guitars and banjos as well as other metal parts [7]

Court transcript noting the difficulty in
acquiring labor in August of 1918. Later mentions
desired wages of $100 per week [7]

Finally with a confirmation of a company and the name in my mind, I went searching for more information and found out that folks on the Unofficial Martin Guitar Forum were familiar with the company and knew them as being pearl inlay manufacturers. Forum users were not convinced that Handel made the tuning machines themselves citing "no evidence" of metalworking but I believe my research confirms that the Louis Handel company produced all parts of the tuning machines

1972 Letter from C. F. Martin III to an anonymous researcher
that attributed pearl inlay production to the Louis Handel company [9]

Previous Questions

Does "Handel" refer to the designer of the buttons or the tuning machines as a whole?

Handel refers to the entire tuning machine assembly from the metal brackets to the famed buttons. They all came from a single company.

Were Handel tuners actually made in Germany? Who made them?

No, from my research it is likely that Louis Handel came from an Austrian immigrant family but his company was based solely in the United States.

The tuners were made by The Louis Handel Company of New York which constructed parts for musical instruments. We can confirm that they were involved with the production of pearl inlays as well as metal working and fabrication which would set them up to construct tuning machines from scratch. I would also say with certainty that they would've had the tooling to produce celluloid buttons 

Why did they disappear from Gibson instruments after 1918?

Given evidence from the court case above, I would say that a shortage of skilled workers and an increase in product costs would've driven Gibson away from the inlaid buttons (assuming Handel was continuing to offer them).