Silver pocket barometer having 1¾” silvered and engraved dial with dual concentric scales, the outer altitude scale calibrated in feet from 0 – 11,000’ and divided to 100’, the inner barometric scale calibrated in inches of mercury with a range from 20 – 31”, divided to 1/10ths. The upper part signed by the maker “L. Casella, London” with the legend “Maker to the Admiralty & Ordnance.” The lower part marked “Compensated” with serial no. “2013.” Rotating bezel with index, blued steel pointer, bevelled glass. Conventional first quality 1” capsule driven movement tensioned on a C spring. All contained within a half hunter semi-barrel form case with engine turned finishers and verso. The inner case back with calibration port, the cover inside with full hallmarks for sterling silver, London, 1874 and the silversmith “JTW.” Extension post and suspension ring. The pocket barometer contained within its correct oxblood leather over timber, green velvet and silk lined case, snap closure on a button release.

Condition: The subject of a full mechanical overhaul and calibration under laboratory conditions. Very crisp, the dial clean and unmarked, the case damage free with good colour, the button a replacement. The movement working well with good sensitivity and progression, accuracy well within acceptable limits, see performance chart.

Comments: This is a particularly nice instrument from one of the leading scientific instruments maker and suppliers of that time. The quality is first class, and the addition of a fine half hunter case by Clerkenwell silversmith James Thomas White elevates it to one of the most desirable of all these instruments. I have handled one other instrument from this series, though this had a rotating verso and was not of the half hunter style.

Very rare, fine and with wonderful aesthetic qualities, this is very much a collector and connoisseur’s piece.