Substantial, first quality Callaghan barometer having 4¼” engraved and silvered dial, the upper portion with barometric scale from 28-31 inches of mercury, numerically graduated to 10^ths of an inch of mercury, annotated “Stormy,” “Rain,” “Change,” “Fair” and “Set Fair.” Signed toward the centre by the maker, “Callaghan & Co.” The lower portion having semi-circular mercurial thermometer with Fahrenheit scale marked 20–120 degrees and Celsius scale marked 0–50 degrees, and maker’s address, “23a New Bond Street, Corner of Conduit Street, London.”

Bold blued-steel pointer with silver-plated telltale, set beneath bevelled glass maintained within a heavy fixed bezel. Conventional single 2½” capsule-driven movement of principally brass construction set on a steel chassis. Bimetallic temperature compensation. The dial verso with novel index drive mechanism having a series of pulleys, the principles set at the perpendicular, connected by a fine waxed cord, the setting crown removable on a tapered square. All contained within a heavy spun case. The dial verso, case, movement and index drive mechanism each struck with no. “5993.”

Clearly manufactured in very small numbers, the assembly number is likely to have been a sequentially designated number fitting in with other production models. The most unusual aspect of this instrument, the index mechanism, is the only such example so observed to date, the more usual system comprising a small gearbox with the drive mounted in the same plane as the dial and engaging with a circumferentially geared altitude or index ring.

The removable setting crown was a feature developed by Callaghan and found in other marine-designated instruments in keeping with general protocols governing the use, keep and observation of ships chronometers which were locked to prevent any unauthorised changes to the ship’s time.

The case retaining much original lacquered finish, the dial near-perfect, the movement with excellent sensitivity and progression. Serviced, calibrated and conserved. A functional, extremely rare and aesthetically attractive instrument. Very much a collector’s piece.

Dimensions: 5½” diameter (inc. suspension post) x 2¼” deep

Stock No: BA0343

Price: Vavasseur Archive