The Hamilton Watch Company increased its production of precision watches following the entry of the United States into the Second World War in 1941. Its 16-size 992b railroad quality pocket watch formed the basis for their Watch, Master Navigational, most of which, 73,285, found their way into Air Force use, while 21,152 were assigned to the US Navy, with 312 going to the Royal Canadian Navy. The movement was designated 4992b. Between 1941 and 1969, when production ceased, about 140,000 had been made. An advertisement in Flying Magazine in February 1948 showed the watch selling new for US$67, while reconditioned ones were available for US$28 or $660 and $266 respectively in 2014 dollars, allowing for a cumulative rate of inflation of 885%. While it retained the fine quality of the 992b, it differed from it in having a sweep second hand , a 24 hour dial reading “GCT” (Greenwich Civil Time which later will become Greenwich Mean Time) and a hacking function, allowing the movement to be stopped easily by pulling out the crown so that the time shown could be set precisely to GMT. It was also up-jewelled to 22 jewels. Pictures 1 and 2 show the layout of the face. The case was generally of chromed nickel silver, though some early ones, made for the Navy, were of silver. Both the back and the bezel screw on. This watch runs well, keeps good time and is in excellent condition, as is the used army metal carry case. There are several Government markings on the case back. Grade: 4992B Manufacturer: Hamilton Manufacturer Location: Lancaster, Pennsylvania Movement Serial Number: 4C119344 Grade: 4992B Model: 5 Estimated Production Year: 1944 Run Quantity: 1500 Total Production: 144,995 Size: 16s Jewels: 22j Movement Configuration: Openface Movement Finish: Nickel Movement Setting: Pendant Plate: 3/4 Plate Adjusted: Yes Adjusted # of Positions: 6 Adjusted to Temperature: Yes Super rare In original U.S. aircraft navigational watch carrying box as pictured. This 22 Jewels 16 Size True WWII Master Navigation Aircraft issue watch. Get a piece of working USA WWII history with this fine working Hamilton 4992B in clean & Good Condition and working great and checked for time keeping. This has the rare US. Gov markings on the case back. Please look at all pictures. Original Dial, Case and Army Aircraft Navigational Carrying Watch Box Please See Pictures Engraved On The Movement GCT Hamilton Watch Company USA. 4992B 22 Jewels Adjusted 6 Positions With Star watch case Co. #R828132, very rare!!! Double Roller On the case back: AN-5740-1; Stock No. 6645-557-0321; MFR'S PART NO. 33106; CONTRACT NUMBER DA-36-038-ORD-20108; SERIAL NO. AF-58-5067; HAMILTON WATCH COMPANY Dimensions: 51.5 mm case diameter; 57 mm to the top of crown; 64 mm to the top of bow; 15.7 mm thickness; 110 gr. total weight. Included is the Original U.S. Army Aircraft Navigational watch case with glass intact as pictured!!!!! WWII 4992B Pocket Watch History During World War II, Hamilton produced a variety of time pieces to support the war effort. In fact, all of Hamilton's production was dedicated to defense purposes. However, they did still produce some wrist watches using excess movements produced in the 1920's. One of the war-related watches was a pocket watch with a central sweep second hand. The movement was based on the 21 jewel, 16 size 992B movement. However, an extra jewel was added to support the second hand pinion, so the movement got 22 jewels and was called the 4992B. The 4992B is known as a "Master Navigator's Watch" as it was used by aviators and navy to aid in navigation. You'll often see 4992B's in a case or a box that was intended to isolate it and protect it from shocks or accidental damage. If you look closely at the dial, you'll see that it's a 24 hour dial so it takes a full day for the hour hand to make a full rotation. 12:00 noon on a 24 hour dial looks like 6:00 on a 12-hour dial. The minute hand still makes it around the dial in one hour, so the ratio of the minute hand to the hour hand is modified using a different minute wheel and hour wheel ratio. Another interesting aspect to the 4992B is it "hacks" or stops when you pull out the crown to set the time. This allows you to set a very precise time... the old, "synchronize your watches" phrase comes to mind.