A mahogany deck box fitted with two brass hinges and a simple pressed brass clip-type catch; the top is glazed with a circular 'porthole' on the upper surface and has a white paper label attached, marked in pen 'SIDEREAL DECK WHATCH (sic) / HAMILTON / AMERICAN LEASE LEND 1940'; in another hand 'Refer to G Knopp' and 'Property of RGO / Archives'. The box is lined with blue velvet in the lid and blue velvet and green baize in the lower half, shaped to the form of the watch. The lid has a folded steel label holder on the inside to hold an issue card.

The bottom of the box is covered with green baize. The chromium-plated nickel, open-face case has the winding/setting crown inset into a wide pendant, with flat, shaped bow. Pulling out the winding button stops the watch (light spring against the balance) and engages the handset facility. The convex 'unbreakable' glass is held in a screw-down, knurled, chromium-plated nickel bezel. The nickel, screw-down back is machine engraved on the back 'NAVIGATION / MASTER WATCH / MFR'S PART NO.3992B / ­ SERIAL NO.1599-1942 / HAMILTON WATCH CO. / H.S.3'. The inside of the back is stamped with the case manufacturer's mark 'KEYSTONE', 'CO' in a shield, 'BASE METAL' and '571074'.

A white enamel dial of 43 mm Æ is signed 'HAMILTON' above the centre. The dial has vertical Arabic numerals, small vertical Arabic five-minute figures round the outside and hours from 13 to 24 within the main hour numerals. Polished and blackened, steel spade and poker-hands have a counter-balanced blackened steel centre seconds hand.

The going barrel, barred movement is of bright, damascened, nickel, and is signed with black enamel-filled engraving on the barrel bridge 'HAMILTON / WATCH CO. / U.S.A' and 'ADJ. TEMP. / AND 6 / POSITIONS'. The escape/fourth wheel bridge is marked '3992 B / 22 JEWELS / U.S. GOVT.'. It is also marked on the main plate, by the balance cock foot '3C1884'. A polished steel index, mounted on the balance cock, acts on a lateral screw for fine rating adjustment, the index has a scale under it, engraved with 'F' and 'S' for fast and slow. There is a four-wheel train with a centre seconds drive off the third wheel and a going barrel.

There is a double roller, jewelled and club tooth lever escapement. The impulse roller has a clear jewelled impulse pin and pallets with clear stones. The pallets bank against brass banking pins. The uncut balance is mounted with 20 brass screws around the rim. The flat spiral, 'Hamilton Elinvar Extra' balance spring, with over coil, has an index mounted on the upper surface of the balance cock. The train is jewelled to the centre (22 jewels in total) with red stones in brass press-in settings. The balance and escape wheel have end stones.

The instrument is in good condition, though the box is slightly knocked and rubbed in places.

The serial number on the box and case (1599) should be the same as Hamilton's serial number for this '3C' calibre movement (i.e. 3C1599). The fact that the movement now in the case is serial number 1884 is almost certainly as a result of movements (all interchangeable with Hamilton material) becoming switched during overhauls at the MoD workshops.