An astronomical regulator in a veneered mahogany case and a flame mahogany panel with a side door in the base. The trunk and a glazed door have fluted canted corners and stop fluting. The under hood and trunk mouldings are concave. The arched hood with circular brass bezel has canted corners matching the trunk.

The 278 mm diameter brass dial is silvered on both sides and has a vertical grained finish. It is laid out in a typical regulator style with concentric Arabic five-minute numerals outside a minute track. Hours are indicated on a subsidiary dial below the centre with Roman numerals within a circle. Seconds are indicated on a subsidiary dial above the centre with Arabic ten-second numerals within a track, and observatory marks at intermediate ten second intervals.

The dial is signed across the centre 'Robert Pennington' and within the hour dial 'LONDON'. The winding aperture is to the left of the dial below the 'o' in 'Robert'. The dial is screwed onto four substantial dial feet pinned into the movement front plate. The hands are of lacquered blued-steel. The central minute hand is plain and retained by a collet and taper pin. The hour hand has a pierced spade with moon counterpoise and is screwed to a brass pipe. The seconds hand is plain with a moon counterpoise and is screwed to a brass pipe.

The eight-day duration, mechanical movement has a brass frame with stepped plates and six, tapering, finned pillars riveted into the back plate. The front plate is retained by taper-pins. Edges of the plates have a curled finish and the entire frame has an orange/pink-coloured lacquer finish. The movement is held to the seat-board by large knurled brass, steel screws fixing into two L-shaped brass brackets on the back plate and a third similar bracket inside the front plate.

The grooved barrel has Harrison's maintaining power and stop-work akin to that found on a fusee driven clock. The sprung stop-iron screwed to the inside of the front plate is activated by the weight line, bringing it into engagement with a stop piece screwed to the front flange of the barrel.

The centre wheel has an extended front pivot onto which fits a cannon wheel. This cannon wheel drives an intermediate wheel of the same number of teeth held by a cock on the front plate, the pinion of which drives a wheel and arbor carrying the hour hand. This wheel pivots in the back plate and in a cock screwed to the front of the front plate, with the arbor passing through a hole in the front plate. Centre, third and escape wheels run in removable brass bushes screwed into the plates. The extended escape wheel arbor protrudes through the front plate and is carried in a bridge screwed to the front plate.

The jewelled pallet frame is screwed to a brass collet on the pallet arbor. The pallet stones are transparent and colourless, possibly agate but are unidentified. The front pallet arbor pivot runs in a brass block screwed and steady pinned to the inside of the front plate. A beat adjustment is via two screws held in a frame screwed to the pallet arbor, which engage with an extended piece above the crutch. The hour and escape wheels are screwed to their collets. The centre and third wheels are riveted to their pinion heads. The pinions are undercut. All the wheels have regulator-style crossings.

The clock is driven by a brass cased lead weight suspended from a (possibly later) brass pulley with six regulator style crossings. The pendulum has a steel rod and frame with a glass mercury jar. It is suspended from a brass Troughton-type 'A' frame support, screwed to the seat board with L-shaped steadying brackets screwed to the backboard. The steel roller suspension has a double-blade spring. An engraved silvered brass beat plaque screwed to the backboard of the case indicates pendulum amplitude.