The Waltham Depollier THERMO has been missing from the historical record for decades. This is the HIGH END version of the Waltham Depollier "Field & Marine" Waterproof Watch. The Field & Marine" was made of nickel. This highly elusive model was named the 1919 Waltham Depollier 'THERMO" Waterproof Watch. The Waltham Depollier "THERMO" Waterproof Watches were only made in .830 silver and 14k solid gold. This is the SILVER version. The side of the case reads "DEPOLLIER WATERPROOF WATCH TRADEMARK". This absolutely remarkable piece of American craftsmanship is in SUPERB condition and has been mechanically restored. Hard to believe that this waterproof watch is 104 years old. All modern dive watches and waterproof watches today can be traced back to these models, the technology developed by Depollier started it all. Our Grandfather's knew how to make things that would last for generations. The movement was just completely taken apart and serviced on 1-18-2022, a brand new mainspring has also been installed. It's in superb running condition and keeping excellent time. This watch has been tested on a professional timegraph 5000 Machine for accuracy so rest assured. Take another look at picture number three again, the 15 jewel movement is clean as a whistle and stunning in its beauty. I'm sure that you have noticed by now that this is not your ordinary trench watch case by a long shot. This is a .830 SILVER waterproof trench watch case that was manufactured by J. Depollier & Son in 1919. The FIVE Depollier patent dates that made this waterproof watch possible are stamped on the inside of the case back, 1916 - 1919. Case number: 289. Years of R&D by Depollier went into this case design. This is a fully hermetic waterproof case so the bezel and case back are both threaded, the threading is in excellent condition! Nobody over the past 104 years has tried to open the case the wrong way by prying it open. So many of these cases have been destroyed by somebody trying to improperly pry the case open but this one is just superb. This case is highly prized by collectors for its beauty & design features and incredible historical importance. This waterproof technology developed by Charles Depollier was tested by Lieutenant Colonel Mauborgne of the United States Army Signal Corps in 1918 and it passed the tests with flying colors. He was the commanding officer of the United States Army Signal Corps Engineering & Research Division when he tested this watch design. The United States War Department would soon thereafter purchase 10,000 of them for the US Army. Lieutenant Colonel Mauborgne would later become a TWO STAR Major General and the Chief Signal Officer of the United States Army. Depollier developed the world's first waterproof wrist watch that actually worked and kept the water out! Plus, this case still has the original factory silver "screw down crown". The case has not been polished, just cleaned. This watch is simply incredible! The enamel dial on this trench watch is among the most desirable that Waltham ever produced, the Shadow Box Military Dial! The dial features a white face, shadow box numerals, outer minute markers, the correct blue steel skeleton hands for this dial and is signed "WALTHAM" near the center. This historic and iconic American trench watch has been fitted with a hand made 16mm tan Khaki Strap and a sterling silver slider clasp that absolutely makes the watch! Take a look at picture number two again, this watch looks stunning on the wrist! The strap will fit a wrist up to 8.5 inches. It will have a bit of wear on it because I seriously could not resist wearing this one for a few days, can you blame me? It's kind of like Ferris Bueller and that Ferrari, if you had access to one would you just leave it in a garage? I think not! Here are the movement details: 1919 Waltham, 15 jewels, size 3/0s, serial number 21413784, grade 365, model 1907. The high end movement features a solid gold center wheel, solid gold raised jewel chatons and solid gold balance wheel screws! They just don't make them like this anymore! The case measures a whopping 44mm lug tip to lug tip, 36mm not including the original factory crown with a nice and wide 16mm lug diameter. The case weighs an incredible 39.6 grams of .830 silver without the movement or 1.39 ounces. That is a lot of silver considering your run of the mill WWI sterling silver trench watch case only weighs about 12 grams. This extremely rare "THERMO" model still has the yellow military crystal. Charles Depollier wrote a booklet back in 1917 titled "The Watch in the Trenches", on pages 13-14 he discusses the need for a dark colored crystal. This was intended to lessen the brightness of the radium lume. You certainly didn't want an enemy sniper taking you out from across "no-man's land". The original dark yellow crystal has some scratches, but nothing that I would consider major. This watch winds and sets exactly as it should and the screw down crown locks into place just as it should! It has no issues. The two shoulders that the crown screws down into are also in excellent condition. This watch is ready to be worn and shown off, it will surely get noticed! I put a lot of time and effort into this Waltham Depollier, I'm sure that you will appreciate the quality and quantity of work that has been done. Solid old World craftsmanship at its finest! You would be seriously hard pressed to find a ANOTHER example of this 1919 Waltham Depollier "THERMO" Waterproof Watch featuring a high end 15 jewel movement, re-lumed shadow box military dial & hands, factory original yellow military grade crystal, screw down crown, Depollier .830 silver case with the five Depollier patent dates stamped into the case back with a hand made tan KHAKI STRAP with a slider clasp, it's the ONLY ONE currently known to exist!