Deck watches have been used as an adjunct to marine chronometers and also as navigational instruments in their own right.
There is some confusion on these. A deck watch was originally used to transfer Time from the chronometer to the deck where it was used to time sextant measurements. The chronometer was kept near the center of the ship to reduce the effect of a rolling and pitching ship and minimize temperature changes.
The US Navy used PS Bartlett and similar stock Watham watches for comparison during the Civil War.
Watches for this purpose did not have to be especially accurate and they did not require much if any observatory testing.
About the late 1890's small fast ocean going vessels. torpedo boats became popular and most services believed their "ride" too rough for a chronometer. They needed what we call torpedo boat watches and the Swiss call a Chronometre de Bord. These were observatory tested but to a bit lesser precision than a marine chronometer. Naval forces e usually bought these by time trial competition until World War II when they needed too many to continue to do that.
The British classed a full marine Chronometer as an HS 1 (HS was Hyrdrographic Stores) HS2 for navigating a torpedo boat class vessel and HS 3 as a comparing watch.
The Hamiliton 21 is an HS1 The 22 and model 36 and model 22 were HS2 and some model 21's and 22's were so issued; aHamilton 4992B's were issued as HS3 as were some similar Elgins
The American watches used for this purpose were primarily made by the Waltham Watch Co, Elgin Watch Co. and the Hamilton Watch Co. with these companies starting production of such instruments around 1910.
Hamilton made two models exclusively for the military deck watch or navigational watch market. The first was the 36 size Torpedo Boat Watch, which was made in response to a government contract RFP. This movement was made in both a flat deck watch form and a gimbaled boxed version. The only variation seen on this model is the absence of an up/down indicator on some examples. At the beginning of World War II, Hamilton introduced the Model 22 Navigational Watch. The model 22 shared many innovations with the larger Model 21 marine chronometer, with an Elinvar hairspring and monometallic balance. It was also packaged as both a flat deck watch and as in a box with gimbals.
Watham's entries were primarily based on their very successful 37 size 8 day watch. This watch movement was used in car clocks, travel clocks and small shelf clocks as well as for navigational watches.
Elgin's entry was a 21 Jewel freesprung up down version of the Father time. It was issued in a small gimballed box, such as were used on U.S. torpedo boats, as well as a large silver case.
The term deck watch is a confusing because it can refer to either a comparing watch or a torpedo boat watch.