An exceptionally good and rare aneroid pocket barometer altimeter no. 6823 by Louis Casella c1885

Pocket barometer having 1⅞” French-silvered and engraved dial, the outer barometric scale calibrated in feet with a range from 0 – 6,000ft and divided down to 100ft, the inner barometric scale calibrated in inches of mercury with a range from 24” – 31” and divided down to 1/20th”. The upper part signed by the maker “L. Casella, Maker to the Admiralty and Ordnance, London” and serial no. “6823,” the lower marked “Compensated.” Fine blued steel pointer, bezel positioned spine index, bevelled glass.

1st quality Vidie pattern movement driven from a single 1” nickel silver capsule and tensioned on a C spring.

All contained within a drum form case, engine turned finisher, the verso with calibration port fitted with screw down cover. Suspension post and bow.

Presented in its original burgundy leather over timber, cream silk and blue velvet lined case, snap closure on a button release.

Condition: The subject of a full service, conservation, and calibration under laboratory conditions. The movement working admirably well across the standard barometric range 28 – 31” Hg, expected loss of accuracy at lower pressures, see performance chart from dynamic test.

Very crisp overall, the dial clean and bright, the original glass chip free and clear. The lacquered brass case retaining virtually all its original finish, some minor oxidation and slight marks. The leather travel case structurally sound with good colour, the cream lid silk with some discolouration, the blue velvet with good colour. Leather replaced over button release.

Comments: One of the finest makers of these and many other instruments besides, easily the peer of Callaghan and JH Steward, and superior to Negretti & Zambra. These instruments are very collectable for their wonderful aesthetic qualities and fine making.

This particular piece might be consider very rare based on its modest serial number and its surviving condition. A very good example of a premier maker’s work.