Pocket altimeter having finely engraved and silvered 2¾” dial, dual-concentric scales calibrated in inches of mercury having a range of 26-31 inches with an altitude range 0–5,000 feet. The outer concentric altitude scale with stations set at 100 feet and divided to 10 feet, the inside edge with corrections, a variation on the Goulier Scale. The inner (stepped) scale displaying inches of mercury divided to 10ths of an inch. The upper portion marked “Compensated,” the lower with retailer’s particulars, “R. Bailey, 14 Bennetts Hill, Birmingham.”
Fine blued-steel pointer, bevelled glass, rotating bezel with index. First quality movement constructed in brass with gilded finish, the bridge piece dated “25.8.09” with finisher’s initials “WB.” Fine set main pivot with relief to chassis (affording greater deflection), primary lever with bi-metallic compensation, fine blued-steel hairspring, the arbour set with narrow journal (affording double rotation). Heavy barrel form case with compensation port to rear set at 7 o’clock, suspension pillar and loop. The whole contained within its original, fine quality imperial purple velvet and cream silk lined pigskin over wood case.
The dial in fine condition, the case retaining the greater proportion of gilt finish, the highly sensitive movement with good resolution and stepless transition, fully serviced, calibration checked. The case in excellent original condition, the pigskin covering still present over the opening button, a sure sign of little use, velvet and silk lining with good colour, losses to leather over the lid. The instrument remains in completely original condition.
A variation – possibly even an improvement – on the Hicks/Watkin patents of the 1880s, this is a more than competent attempt to produce a more open scale in a modestly sized instrument. The draw back is that, unlike the Hicks/Watkin, there is no means of knowing from the dial which of two possible readings should be taken. The movement, though unsigned, is the work of Short & Mason. It is specifically designed for its application, unlike other multiple rotation movements that are noted to have been single rotation movements with modifications. This instrument thus afforded sufficient resolution to be both practical as an altimeter and barometer.
An impressive instrument in the hand, this pocket barometric altimeter has very good aesthetics – the condition is wonderful and the added dimensions of its rarity and complication make this a prime collector’s piece.
Dimensions: 3½” diameter x 1½” deep
Stock No: PB0390
Price: Vavasseur Private Collection
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