Explorer’s Travelling Aneroid Barometer Altimeter c.1890

A good cased explorer’s travelling aneroid barometer altimeter c1890. Aneroid barometer having 3¼” silvered and die struck dial, the outer altimetric scale calibrated in feet with a range from 0 – 16,000ft, divided down to 100ft, following the Airy Scale, the barometric scale calibrated in inches of Hg with a range from 16" – 31" and divided down to 1/10th", the upper part marked "Compensated." Rotating bezel with index, blued steel pointer, bevelled glass. Driven from a single 1¼” nickel alloy capsule tensioned on a C spring. All contained within a lacquered brass drum form case, extension post and suspension ring. Calibration port to verso. Presented in its original leather effect brown over timber, grape velvet lined travel case, snap closure on a button release. Condition: The subject of a full, service, conservation, and calibration under laboratory conditions, the movement working exceptionally well across the normal barometric range and down to 20” or around 11,000ft, see performance chart. The dial with some fine abrasions only visible in critical light, otherwise clean and vibrant. The lacquered brass case retaining much of its original finish, light wear and abrasions to verso, points of oxidation. Comments: Unsigned, but almost certainly by Negretti & Zambra. By no means a rare instrument, though the condition of this particular example with its original travel case does make it quite exceptional and certainly collectable.