Hamilton 4992B. Silver Case. Original Deck Box. Superb!

Fabulous deck watch / Master Navigation watch with original box made by Hamilton Watch Co. in 1941.
 
The 4992B watch was made specifically for the military only during the 2nd. World War period. The nickel movement was a development of the 21 jewel 992B railroad watch which was adapted to run with a centre seconds sweep hand and to include a hacking feature. The centre seconds hand required an additional jewel to support it thus raising the overall jewel count to 22 jewels.
The movement is state of the art for the time and had 22 jewels, a fully capped Swiss Lever escapement with double roller, Sapphire pallets and gold timing screws with a sprung micro-regulator. The movement also features the revolutionary "Elinvar" hairspring with associated solid mono-metal balance wheel. This hairspring is resistant to temperature changes and is also anti-magnetic. The watch was fully adjusted for timekeeping accuracy in 6 positions.
This watch is running really well and is keeping really good time within a couple of seconds per 24 hours. The watch is stem wind and stem set. Pulling the crown to set position operates the Hacking feature whereby the watch stops, depressing the crown to run / wind position allows the watch to restart. 
 
The watch case is made from 0.800 grade solid silver and has screw on / off front and rear covers. Both covers remove easily and replace easily with care to close down square and tight all around.
 
The black painted metal dial is a true 24 hour dial and the watch is designed such that the hour hand revolves once in 24 hours rather than the conventional 12 hour revolution. So the 6 is where you may expect to see the 3 and the 12 is where you may expect to see the 6. This was a US military requirement and I have no idea why as the watch is not intuitive to read but hey ho!
The dial is in super condition  with all of the printing crisp and clear. White enamelled hands indicate the time under a very good acrylic crystal.
 
Overall a very desirable military timepiece in super condition in the rare silver case, and all working as intended.