Spring Detent Chronometer

The point of this watch is under the cock. Where a lever watch carries a flat spring, this one carries a blued steel helical spring standing on the balance staff in a small coiled column, and beneath it a spring detent that releases the escape wheel once for every swing of the balance in one direction only. Wound and set down, it does what a chronometer does: the seconds hand steps forward in halves, a distinct beat with a pause in it, and the balance, a cut bimetallic rim carrying its timing screws, swings wide and slow. It is the escapement of the ship's box chronometer, scaled to the pocket.

It was made on the Continent in the second half of the nineteenth century, in the years when the English market bought chronometer-grade movements from the Swiss workshops and had them finished and signed for London. The frosted gilt three-quarter plate, the screwed gold chatons, the long tapered cock with its Breguet-style index, and the plate signed in copperplate script, Frodsham, London, N° 1000, all belong to that trade. The regulator is engraved Fast and Slow in English, for an English hand. The Frodsham name was the one such work was most often given, and this watch carries it in the form the trade used: surname, city and number, nothing more.

The dial is the London style of the day, white enamel with black Roman numerals, an outer minute track with Arabic figures at the fives and a sunk seconds ring at six. The spade hands are blued steel, oxidised now to a deep plum; the seconds hand is gilt. The face is bright and clean, with a single faint mark out near the 3 that reads as surface rather than damage.

The case is the one the movement was born in: an open face in white metal, 50.95mm across, with a hinged bezel, a hinged back and a cuvette pierced for the two keys, unmarked in the continental way. It shows light scratching on the back and a touch of verdigris at the bow joint, and closes as it should at bezel, back and cuvette. The pendant carries a smooth knob and an oval bow; the winding is done through the back.

Chronometer escapements in pocket watches were never common, and most that survive are English work in hallmarked silver or gold. This one came by a different route to the same market, with the same escapement, the same helical spring and the same compensation balance, and it is still doing the job it was built for. The marks, the movement and the condition are set out in the drawers below.