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 "Navigator's Watch" as it was used by aviators to aid in navigation by the US Navy during the war.
Here's a couple of advertisements from WWII-era Life Magazines that featured the 4992B.
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.