A three-tier, brass-bound, mahogany box with pressed brass sliding catch on the front for the lid and for the upper half. The lid of the box has a strut allowing it to open to 90° only, and the brass piano hinge has a removable pin allowing the lid to be removed altogether. Inside the lid is a folded, brass-plated steel label holder without a card. On the front of the upper half is a rectangular black plastic plaque with rounded ends, printed in white with the signature 'HAMILTON WATCH CO. / LANCASTER. PA., U.S.A.'. Below this is a black, laminated plastic label engraved through to white plastic, with the figures 'No. 3653'. The box has a brass beading running along the centre of the junction on the lower half, mating with a groove in the junction of the upper half and forming a dust seal when closed.

The box fittings are standard, with brass drop handles on the sides and lacquered brass gimbals. The upper half is on a brass piano hinge with a removable hinge pin and a strut allowing it to open to 90° only, but the strut has an opening in the slot to allow it to be disengaged so the upper half can be opened right over or removed. Inside the back of the upper half is a black-lacquered aluminium label printed in silver with 'MINISTRY OF DEFENCE / HYDROGRAPHIC DEPT. / CHRONOMETER MARINE / Stores Ref. H.S. 527-3634 / Serial No. 3653'. The serial number is engraved through to bright aluminium. The interior fittings are otherwise of a standard layout, with a standard pattern rising ratchet-winding key, engraved '3653'. Fixed at the back, on the bottom of the lower half, is a rectangular white plastic plaque with rounded ends, printed in black with the signature 'HAMILTON WATCH CO. / LANCASTER. PA., U.S.A.'. Below this is a black, laminated plastic label engraved through to white plastic, with the figures 'No. 3653'. The underside of the box has a green baize covering.

The matt-silver-finish dial is 104 mm Æ, with all markings etched and filled with black enamel paint, and is attached to the brass edge from the inside with four screws. The movement is attached to the brass edge with three nickel-plated screws. The dial has vertical Arabic hour numerals and a large seconds dial has Arabic ten-second figures with straight batons at alternate five-second intervals.

The dial is signed in the centre 'HAMILTON / LANCASTER, PA., U.S.A.', it is numbered 'N3653', and marked (date of contract) '1941' within the seconds dial. The up and down dial, below 12, is marked in Arabic in eight hour intervals: '8 [to] 48'. It is marked 'UP' before eight and 'DOWN' after 48. Black patinated steel spade and poker-hands have a fine, black patinated pointer seconds hand with a counter-poised tail and a black patinated up and down pointer.

This is Hamilton's version of Nardin's standard M. G. F. type, two-day, solid nickel alloy (employing some copper and zinc), full-plate fusee movement with four pillars, all fixed with polished nickel-plated screws. The general level of finish of the movement is very high with all movement parts damascened. The pillar plate is engraved '2E3653' and the upper fusee/barrel plate is engraved 'MODEL 21, 14 JEWELS / HAMILTON WATCH CO. / LANCASTER. PENNA. / MADE IN U.S.A. / N3653-1941'. The fusee, which has a brass cap, continental stop-work and Harrison's maintaining power with a brass ratchet wheel, has a pipe round the winding square and a plastic seal above.

The inverted barrel and cap, which is secured with five screws into the edge of the barrel wall, are both in brass and the set-up ratchet wheel and click, mounted under a bridge on the upper plate, are in steel. The barrel has a fixed steel hook and an additional steel-hooking piece in the barrel at the outer terminal of the mainspring, for protection of the hooking. This piece runs just under three quarters of the way round the inside of the barrel. A fixed hook in the mainspring proper locates in a hole in the piece. The mainspring is unsigned. There is a four-wheel train with a great wheel. The wheels are gilt brass and the third wheel-run is within an opening in the pillar plate on a third/fourth wheel-bar. Where pivots are not run in jewel holes they have gilt-brass bushes in the nickel frame.

There is an Earnshaw-type spring detent escapement with a white metal (possibly steel) detent mounted on a nickel block on the potence plate. The detent has a bifurcated spring and a screwed-on, Elinvar passing spring cranked out to run parallel to the detent blade, and a red jewelled locking stone. The impulse roller has a radially set, red impulse jewel and the discharge roller has a similar stone inset.

The two-arm Hamilton 'ovalising' balance has straight, narrow arms (invar) and the rim (stainless steel) has four, brass compensation screws on each side. Nickel-plated steel, meantime nuts are mounted on fixed threads at the end of the arms. There are small, nickel-plated steel 'vernier' meantime nuts mounted on the rims just to one side of the balance arms. The polished, 'Elinvar Extra' helical balance spring has terminals on both ends. The upper terminal has a stud fixed under the balance bridge. The jewelling, which is mounted in brass or nickel settings, extends to the balance and escape wheel with end stones, both holes on the fourth, the lower third pivots and the escapement parts as mentioned.

The movement is in fine, almost new condition, though the mainspring appears to be broken. The box and gimballing have been rather roughly refinished and re-lacquered in recent years.