Box/Mounting The timekeeper is housed in an outer, two-tier square mahogany box, of dovetail construction, measuring 141mm high, 203 wide and 186 deep. The top surface of the upper section is inlaid with a lozenge-shaped ebony plaque. Inside the upper section there is a block in the rear left which is hollowed out to receive something, possibly the winding key, for storage. The arrangement is however incomplete and the current winding crank does not fit well in the recess it provides. There are also screw holes and a small hollowed out recess in this area which suggest there may have been a small thermometer fixed in the back of the upper section originally. There are marks and the residue of old glue inside the front right of the upper section which suggests another piece fitted here at some stage. The upper section opens right over and rests on the table. The lower edge of the upper section has a strip of blue baize stuck along it, forming a dust seal with the lower section when the box is closed. The base of the box is covered with coarse green baize.

The lower section has simple brass drop handles on the sides and a narrow brass escutcheon lining the keyhole on the front. Mounted on either side on the inside of the lower section are curved brass arms, terminating in trunnions upon which the internal box for the timekeeper is pivoted, enabling it to swing over from front to back. A brass latch, mounted on the inside of the right brass arm, engages with a double-ended brass piece on the internal box, and secures the internal box in one of two horizontal positions: dial facing up or dial facing down. The fine and delicate winding key is in brass, with an ivory handle, and is of the crank type. The key is also of the ratchet type, a set of mating ratchet ‘crown wheels’ on the shaft of the key allowing only clock-wise rotation.

The two-tier internal box is also in mahogany, and is externally of octagonal shape, but circular inside. It measures 140mm across flats and is 59mm high. The eight sides of the upper section are joined round the top with a circular brass ring, veneered under with satinwood, and screwed down into the top edge with eight brass screws. The sides are probably also connected inside each adjoining face with a hidden inserted slip. The eight sides of the lower section are probably also joined with hidden inset slips near the upper edge, but also have joining slips, morticed into the lower parts of adjacent sides, which are visible from inside the box. The two mating faces of the two sections of the box are veneered with satinwood. The base of the box is covered with an octagonal lacquered brass plate, fixed up into the sides of the box with eight brass screws, and engraved on the underside: 326 / Barraud, / Cornhill, / LONDON. The plate is also marked in ink: SII317 and is scratched: 6/55 / 4. Off-centre on this plate is a revolving brass shutter for the winding hole. A single, seven-knuckle brass hinge on the rear of the box is fixed to the upper and lower sections, each with three brass screws threaded into brass sockets, inserted into the wood of the rear sides of the box. The inside of the box is painted with black lacquer and there is a brass upstanding peg at the back of the lower section, at the 60 minutes position, on which the glazed-brass timekeeper case locates. The box closes with a brass hook on the lower section engaging under a shoulder screw on the front of the upper section.

Inner Lock However, the box can also be more securely closed with a special brass lock on the front of the lower section. A single pierced peg, projecting down from the upper section, enters a hole in the lock in the usual way, while two brass pins, on either side, also projecting down from the upper section and entering holes in the edge of the lower section, positively locate the two sections together. The rectangular keyhole for the lock is in a swivelling boss, mounted at the centre about which the brass hook swings, the boss revolving independently of the hook. The lock has the unusual feature (perhaps unique?) of enabling locking without a key, but unlocking can only be performed with the key. A simple clockwise turn of the boss using any rectangular-section, peg-like implement inserted in the rectangular keyhole and turned, will throw the bolt inside the lock into the locked position. However, as the bolt moves into the locked position, a latch inside the lock drops behind the bolt and the lock cannot then be unlocked by simply turning the boss in an anti-clockwise direction. For unlocking, a special key has to be inserted and turned. This key, which is also of simple, rectangular, peg-like section, has pivoted on its end a small steel part. This normally forms a part of the simple rectangular peg, but when the key is inserted and the handle of the key is turned, the steel end of the key revolves first, about 50°, independently of the rest of the ‘peg-like’ end, and releases the latch. Continuing to turn the key then revolves the central brass boss and causes the bolt to withdraw. When the timekeeper was first received at the museum there was no key for the lock. Fortunately it was not locked and dismantling and study enabled a key to be designed and made (2008). Such is the unique design of the lock that the original key is unlikely to have differed in any material way from that which is now with the timekeeper.

There are three drilled dots on the front of the boss of the lock, also under the top brass ring and under the brass base plate. The hinge and adjacent woodwork, and the brass trunnion plates on the sides of the box, are all marked III.

The inner, glazed brass case of the timekeeper is in the form of an eight-pillar, glazed drum, and with a fixed, flat glazed base. The eight turned pillars have flat glass panels between them. Over the top of the case, there is a shaped, moulded brass bezel with a convex glass protecting the dial. The bezel is mounted on a single, five-knuckle hinge at the 60 minute position and hinges open to allow access to the hands. Brass dog-screws at the 15 and 45 minute positions on the dial, when turned through 90 °, release the movement-securing dogs, and allow the movement to be taken out of the glazed case. The bottom moulding of the brass case is marked with three drilled dots on its lower edge. A lacquered brass ring, secures the flat glass panel in the base, and is fixed to the bottom moulding from below with six dot-marked brass screws. The ring is marked in small ink script: 425. The glass panel in the base is mounted with an off-centre gilt-brass swivelling shutter for the winding hole.

Dial & Hands The 102.7mm Ø gilt-brass dial plate, which is stamped on the rear: 6, has two low convex white enamel plates attached, one for hours and minutes in the upper part of the plate and one for seconds below. The gilding of the dial plate runs just round onto the back, but is left ungilt beyond the edge. Both plates are retained with a finely moulded, narrow gilt-brass ring, each ring scratched on the underside: 6, and secured from behind with three and four small brass dot-marked screws for seconds and hours dials respectively. The seconds dial is marked in ink on the counter enamel: 6. The dials are flanked to left and right by finely chased, cast silver spandrel decorations, both scratched on the back: 6. The hours dial has 12 arabic numerals and small arabic five minute figures outside the minute circle, and the seconds dial has arabic five seconds figures. The dial has finely polished blued-steel beetle and poker hands and a blued-steel pointer seconds hand with a counter poised tail, gently curved to match the shape of the convex enamel dial plate.

Movement The full-plate, gilt-brass, reverse-fusee movement has four turned pillars terminating in shaped and nicely moulded round feet. The pillar plate is gilt on the upper surface but only runs just round onto the underside and is ungilt beyond the edge. The potence plate, which is engraved: Barraud, / Cornhill, / LONDON / 326, is pinned on. The general level of finish of the movement is exceptionally fine, with all brass frame parts fire gilt, all wheels and other non-gilt brass-work finely polished and steel parts given a fine even grain. All the larger screws in the movement are in brass. The upper surface of the pillar plate and the underside of the potence plate are stamped: 6. All the original holes in the frame from the earlier Mudge escapement are still present, though the original engraving on the potence plate has been erased (traces remain) and the plate was re-gilt after engraving with the current signature.

The movement incorporates a resting barrel mounted on the underside of the potence plate. The barrel has ratchet teeth cut on a flange round its upper edge, for setting up the mainspring (but remaining stationary thereafter), the teeth acting on a brass click also mounted on the underside of the potence plate. The barrel is fixed to the potence plate with a circular brass disc, rebated inside the top of the barrel. The disc can be screwed securely to the underside of the potence plate, and the barrel can thus revolve round it (when setting up the mainspring), while the stepped rebate on disc/barrel prevents the barrel from coming away from the plate. The barrel has a rectangular hooking hole which is cut in the wrong direction for the hook, apparently from new, and is redundant, a correctly orientated hole being cut at 180° to it, in the barrel wall. There is a lower cap to the barrel, with a central hole allowing for insertion of the barrel arbor, the cap snapping on after the mainspring has been fitted but before the barrel arbor.

The barrel arbor runs on pivots between the plates. The arbor is integral with the chain barrel and when it is put into the standing barrel the chain barrel encloses the mainspring barrel inside it. The reversed fusee has Harrison’s maintaining power, and a separate steel cap with stop-work hook, secured with two screws. There is a brass, straight-sided fusee pipe screwed to the potence plate. The great wheel and maintaining wheel are retained on the fusee arbor with a steel friction-fitted collar having a squared end for twisting the collar onto the arbor. The balance cock is scratched 6 under the foot. The drive to the motion work is taken off the extended pivot of the centre wheel, upon which is pinned on the friction-mounted minute wheel and pinion, under the dial. The minute wheel has no friction spring under it, the close fit on the extended pivot providing the friction clutch for hand setting. The minute wheel meshes with the cannon wheel and the minute pinion meshes with the hour wheel, which is mounted on a brass bridge over the cannon wheel.

There is a four-wheel train plus great wheel, the train running in the reverse direction from the conventional arrangement, and the fourth wheel incorporating a separate reverser for the seconds hand. The centre wheel is very slightly tapered in thickness towards the rim, and the third wheel is distinctly tapered in the same way. The escape wheel is run between the potence plate and a potence mounted on that plate.

Escapement, Balance & Spring and Jewelling The Arnold spring detent escapement (almost certainly made by Pennington) has the detent set into a slot in the potence plate, and with the discharge roller above the impulse roller on the balance staff. The escapement is pitched in Arnold’s usual way, with the impulse faces of the teeth only half engaged with the impulse pallet on the roller. The impulse roller has a radial red impulse stone inset, and the discharge roller has a small red pallet stone inset. The steel spring detent has a steel passing spring riveted to its side and has a pink, rectangular section locking stone set into it. The detent stops against an adjustable red alloy (bronze?) banking piece set alongside the slot in the potence plate

The two-arm Arnold-type bimetallic balance has tapered arms in a reddish alloy (bronze?) and brass and steel bimetal rim segments screwed at the ends of the arms in the typical Arnold style. At the ends of the arms are brass mean-time screws threaded in the rim. The rim segments extend to 90° from the arms and have brass compensation nuts on curved steel threads at the ends. The blued-steel helical balance spring has terminals on both ends, the upper terminal attached to a brass stud notched into the top of the balance cock. The jewelling extends to the balance, escape wheel and fourth wheel with endstones, and the escapement parts as mentioned. The upper balance pivot now has a ruby endstone in a brass setting, fixed within the remains of the earlier blued-steel setting.

History The earliest known information concerning this chronometer is that it was in the possession of the academic chemist C.R. Bury (1890-1968) in England during the 1930s. It is not known how he acquired it, but on his death it passed to his son John Bury. In the autumn of 2001 the chronometer was taken along to one of the BBC’s Antiques Roadshow programmes being held in Stroud in Gloucestershire (UK) and was identified by the expert Simon Bull as a Mudge-type timekeeper on the programme [FN: Betts, Jonathan, ‘The Roadshow Chronometer’, HJ, August 2002, p.276.]. Subsequently the chronometer was taken on loan at the NMM, and is now bequeathed to the NMM’s collection.