A mahogany deck box with a circular ivorine tablet inset into the top. It is engraved 'C­W / NARDIN / No. 29557', and is fitted with a nickel-plated brass piano hinge and a simple nickel-plated sliding catch. The box is lined in the base with red velvet and contains a brass drum mounting, lined with red-velvet-covered cork, shaped to the form of the watch and lined, having a brass screw-down bezel with a silvered site ring and bevelled glass. The lid contains a brass-plated, folded steel label holder for an issue card and a black-painted aluminium label, marked in silver 'MINISTRY OF DEFENCE / HYDROGRAPHIC DEPT. / WATCH CHRONOMETER / Stores Ref. H.S. 527-3636 / Serial No. 29557'. The serial number is engraved through the surface to bright metal.

The bottom of the box is covered with green baize. The silver, open-face case has the winding/setting crown inset into a cylindrical pendant, with a hand-setting push piece on the side of the case to the left at '11 o'clock'. The plain silver, rolled-edge bezel has no fitting for a glass. The screw-down back is machine engraved on the back 'H.S. ­2' and is stamped inside with the manufacturer's mark 'ULYSSE NARDIN / LOCLE' in Nardin's emblematic shield, the incuse number '601967', scratched under '29557', a separate octagonal cameo 'Canard' (Swiss control mark for silver) mark, including the L for Locle, and, within rectangular marks, '0.925' and 'FFBA / 46'. The band of the case is also stamped '967'.

A white enamel dial of 50 mm Æ, is signed 'ULYSSE NARDIN / LOCLE / 29557 / C­W' above the centre. The dial has Roman numerals, and small Arabic five-minute figures with fifth-of-second marks round the outside. Blued-steel, spade and poker-hands have a counter-balanced blued-steel, centre seconds hand.

The going barrel, barred movement is of matt-gilt brass, and is signed with machine engraving on the barrel bridge 'ULYSSE NARDIN / SWISS'. It is also marked on the main plate, by the escape wheel cock foot '29557' in a rectangular surround. A polished steel index, mounted on the balance cock, acts on a horizontal steel screw for fine rating adjustment, the cock having a scale engraved on it, with 'F' and 'S' for fast and slow. There is a four-wheel train with a going barrel and a centre seconds drive off the third wheel.

There is a double roller, jewelled and club tooth lever escapement. The impulse roller has a jewelled impulse pin and pallets with red stones. The pallets bank against brass banking pins. The cut bimetallic compensation balance is mounted with 18 brass screws around the rim. The flat spiral, blued-steel balance spring, with over coil, has an index mounted on the upper surface of the balance cock. The train is jewelled to the centre with red pressed-in stones; the balance and escape wheel have polished steel-set end stones.

The instrument is in fine condition, with just a few marks on the wooden box.