A very good and characteristically unusual aneroid pocket barometer altimeter no. 531 by Negretti & Zambra, London, c1940

Pocket barometer altimeter having 1⅞” silvered and die struck dial, the outer bezel driven altitude ring calibrated in feet with a range from 0 – 20,000ft divided down to 100ft on the Airy’s scale. The inner barometric scale calibrated in inches of mercury with a range from 15” – 31” divided down to 1⁄10”. The upper part marked “Compensated,” the lower signed by the maker, “Negretti & Zambra, London” with serial no. “531.”

The standard movement driven from an ‘improved’ flux-welded 1¼” capsule tensioned on a C spring. All contained within a lacquered brass drum-form case, calibration port to verso, extension post and bow.

Presented with its correct burgundy leather over timber, deep blue velvet and purple silk lined round case, snap closure on a button release.

Condition: Fully serviced, conserved, and calibrated under laboratory conditions, the movement accurate to 1⁄10” across a very wide scale, see performance chart.

Difficult to fault, this is in really beautiful condition with very clean undamaged dial, the case retaining virtually all its original lacquered finish, minor marks and small points of oxidation. The travel case structurally sound, retaining a good degree of its original finish with excellent colour, the fabric interior bright and vibrant.

Comments: This is a very interesting instrument, perhaps the culmination of pocket barometer making expertise: the dial with a significantly different though clearly original finish; the capsule, of the finally evolved pattern of flux welding and potentially of pressed and hardened steel construction, has clearly contributed greatly to the accuracy of the overall design which by any standards must be considered noteworthy; and the presence of a low serial number despite a date of manufacture of c1940 that suggests this is part of the last, or one of the last, sequence of aneroid pocket barometer altimeters.