Hamilton 4992B Master navigation Watch

A military grade pocket watch made by Hamilton Watch Co. in 1941.
 
The military specification 4992B was produced by Hamilton by using the well renowned 992B railroad watch as a base and modifying it to have a centre seconds sweep hand along with a "hacking" feature. The gearing that drives the hands was also modified such that the hour hand revolves once in 24 hours rather than the conventional once in 12 hours. The inclusion of the centre seconds hand meant the addition of one extra jewel which raises the total jewel count to 22 from the 992Bs 21. The 4992B proved to be so accurate and reliable that they were called "Navigation Master Watch", being so accurate that they were good enough to use for navigation purposes, and also good enough to be used as the "Master Watch" within a unit such that all other timepieces within that unit were set from, and synchronised to the "Master Watch".
The watch is stem wind and stem set, pulling the crown to set position stops the watch which allows for precise time setting and easy synchronising with others as pressing the crown to run position immediately restarts the watch. This is the "hacking" feature.
 
The movement has 22 jewels, a fully capped Swiss lever escapement with double roller, Sapphire pallet stones, gold timing screws and a micro-regulator. The movement also has the "Elinvar" temperature resistant hairspring and accompanying solid mono-metal balance wheel.
This one is in beautiful condition mechanically and cosmetically. It is running strong and keeping spot on time.
 
The 3 piece case is made from plated base metal and is in unmarked condition with both covers removing and replacing easily, and no loss of plating. Please see the photos to judge the condition.
 
Original black painted metal dial is flawless. This is a true 24 hour dial with the 12 in the position you would normally expect to be the 6. Outer 60 seconds track.
Excellent set of white painted hands under a very good acrylic crystal.
 
Overall, perfect. If you are looking for one of these then this could be the best you will find.