A good WWI “Luminous” Aircraft Altimeter Mk IVA No 34539A by Short & Mason Ltd c1918

Aneroid aircraft altimeter having 3⅝” japanned stepped dial, wheel rotated outer part marked “Thousand Feet”, altimetric scale calibrated in feet with a range from 0 – 10,000ft divided to 200ft, instrument serial “No 34539A” at 6 o’clock. The centre marked “Height” and “Mark IVA, No 34539A,” “Luminous,” and “Short & Mason Ltd.” Part japanned and part luminised pointer, reverse bevelled glass.

The first quality japanned movement of basic Vidie pattern driven from a single 2” soldered capsule and tensioned on a C spring. The movement dated “16/9/18,” and both the chassis and movement struck “M.” All contained within a flanged drum form aluminium case, the verso struck “A” over broad arrow government ordnance mark.

Condition: The subject of a full service, conservation, and calibration under laboratory conditions, see performance chart from dynamic test. The movement with good sensitivity, very accurate over the first 4,000ft with small incremental drift toward the lower pressures, entirely consistent with the majority of antique instruments of this age.

Overall very crisp, the dial with minor marks only, ageing and losses to luminised scale and pointer, altimetric outer part moving smoothly with correct resistance.

Comments: These instruments were no more than an adaption of the aneroid barometer – that said, the association with a fascinating chapter in the history of flight and aerial warfare sets them very much aside as extremely desirable collector’s pieces. A number of variants are known – this example would appear to be one of the least common and perhaps aesthetically one of the most attractive. The movement is of super high quality and made to the highest standards of the time.

Very much a collector’s piece.