Pocket barometer altimeter having die struck 2¾” silvered dial, the outer scale divided with stations at thousands of feet subdivided to hundreds of feet and having a range from 12,000 – 25,000 feet. The inner scale divided into inches of mercury further subdivided to tenths of an inch with a corresponding range from 20 – 12 inches. The upper dial marked “Compensated,” the lower with maker’s logogram “Casella, London” and serial no. “11052.” Fine blued steel pointer. All set beneath a bevelled glass maintained in a rotating bezel with fine index.
High quality specially constructed 1¾” capsule driven brass movement finished in frosted gilt lacquer, contained within a substantial chrome plated drum form case. The verso inscribed “Royal Geographical Society No 59.”
These instruments, made specifically for the Royal Geographical Society, were delivered in only small numbers. This particular piece will not register at altitudes below 12,000ft, thus enabling a more open scale for the indicated range. Additionally, due to the short comings inherent in the aneroid system, it is easier to produce more accurate readings over shorter ranges – thus a wider scale with a closer range is more desirable.
Minor losses to dial, some wear to chromium finish.
The Royal Geographical Society currently carries altimeter inventory no. 58 by Casella as part of their collection.
Dimensions: 2¾” diameter x 1¼” deep
Stock No: PB0554
Movement under test in our pressure chamber, showing smooth and progressive transition down to 12,000 ft