The Vacheron Constantin U.S. Army Corps of Engineers Pocket Watch is a highly collectible piece of military horological history. Commissioned by the American Expeditionary Forces (AEF) during World War I and delivered into the early 1920s, this 52mm solid silver manual-winding timepiece was designed specifically for high-precision military operations, such as supervising tactical railroad networks in France.

The AEF originally contracted Vacheron Constantin to produce 5,000 of these chronographs. However, because production ceased shortly after the war ended, only 3,289 pieces were actually delivered, making intact surviving examples exceptionally scarce. 

The dials were custom-stamped with "Corps of Engineers U.S.A. / Vacheron & Constantin Genève". To make them usable in dark trenches and night operations, the numbers and skeleton hands were originally painted with radium-based luminescence.

• Case Size: 52mm diameter, offering extreme field legibility. 

• Case Material: 0.900 Fine Silver (Continental Silver standard) featuring a hinged case back and interior cuvette.

• Dial: White porcelain enamel featuring large bold Arabic numerals, cathedral/skeleton hands, and a subsidiary seconds dial at the 6 o'clock position. 

• Movement: Manual-winding Caliber R.A. 19/20''' (featuring an ébauche initially sourced from LeCoultre), built with 15 to 20 jewels, a bimetallic balance, and mercuric gilt-finished bridges. 

• The Chronograph Function: Most variants are mono-pusher chronographs, where pushing down directly on the crown starts, stops, and resets the central sweep-seconds chronograph hand. A rare few "time-only" variants are also known to exist.