Pocket Barometer Altimeter by Negretti & Zambra No 20210 c.1910

An unusual good oxidised brass aneroid pocket barometer altimeter by Negretti & Zambra, London no. 20210 c.1910. Pocket barometer having 1¾” silvered and die struck dial with outer crown operated altitude ring calibrated in feet with a range from 0 – 10,000ft divided down to 100ft, inner barometric scale calibrated in inches of mercury with a range from 21” – 31” divided down to 1/10th. The upper part marked “Compensated,” the lower signed by the maker “Negretti & Zambra, London,” and serial no. “20210.” Fine blued steel pointer, bevelled glass, pendant and bow with brass crown. The standard configuration movement driven from a single 1” nickel alloy capsule and tensioned on a C spring. The whole presented within an oxidised brass ribbed semi barrel form case, calibration port to verso. Condition: The subject of a full service, conservation, and calibration under laboratory conditions. The movement working well with easily acceptable accuracy across the scale, see performance chart. The dial clean and crisp, some minor marks and slight staining at one point on altitude ring. Small repair to gear on altitude ring. Brass case retaining most original oxidised finish. Comments: An unusual pattern. Of particular interest is the dial with its turned down periphery creating a circular seating for the revolving altitude ring, a design feature not seen before. An interesting and aesthetically appealing instrument in really much above average condition.