This is a nice example of the Wrist Compass issued to US Paratroops. It was also a part of some of the "Escape and Evasion" kits issued to USAAF Combat Aircrew. Made by Superior Magneto Corp., and marked "5-44". I see some listings mention water-filled, although I don't see any indication there was ever a liquid inside. Unlike most surviving originals, the dial on this one moves freely.