Antique lacquered brass French aircraft altimeter having 3¾” die-struck silvered brass dial with twin concentric scales, barometric pressure and altitude, the outer, altitude, rotating from the crown with a range from 0–2,800 metres with stations at 200 metres, 1000 metre stations in red, resolution 20 metres. The inner barometric scale graduated from 56-78 cm of mercury. The upper centre dial marked Naudet & Cie with “PHNB” logogram and “Paris”, the lower part with instrument serial no. “311” and “Aviation Militaire.” Broad blued-steel pointer set beneath bevelled glass. Conventional barometer type 2” capsule driven movement tensioned on a C spring, chassis, bridge primary lever and cock in the manner of Negretti & Zambra, the cross shaft sub-assembly with kinetic mass appearing as a Naudet modification. The whole raised on a substantial circular cast steel chassis. Drum pattern case having ribbed circumferential decoration, altitude correction crown, calibration port to verso.

Contained in its correct brown leather and maroon velvet-lined flight case, the circumference of which bears four D rings, the back secured on popper studs and short leather straps.

Condition: The dial with clear signs of age, the centre with minor marks only visible in critical light, some further areas of oxidation, otherwise appearing crisp. The altitude scale operates from the crown as it should, though there is a pronounced high spot at which point rotation becomes more difficult. It is recommended that the crown is rotated clockwise as viewed from on top. Some old re-silvering with losses and very minor area of distortion.

The brass case retaining a good proportion of original lacquered finish. Noteworthy are two pronounced scorch marks to the verso with an associated slight depression to the verso edge. Otherwise crisp.

The movement with good sensitivity, stepless progression, better than might be expected accuracy – see performance chart below. The manufacture of this movement is most interesting – it bears many of the hallmarks of Negretti & Zambra but with the clear addition of refinements in the cross shaft consistent with Naudet. Possibly explained by war shortages, nonetheless this is a perfectly valid movement, with an almost identical one logged to Naudet Aircraft Altimeter No 768.

The flight case complete, the leather in essentially fair condition, marks abrasions and losses, one securing strap at fault. The velvet lining with good colour and in good condition.

Comments: It is not so often that we are able to offer such interesting pieces as this, an early aircraft altimeter issued to the fledgling French air force (“Aviation Militaire”) sometime around the outbreak of hostilities. The maker Naudet being one of the pre-eminent maker of aneroid barometers in the world at this time. The association with early wartime flying is compelling and one can only wonder at its history. It is fairly clear that this instrument was in an aircraft that crashed and burned, the leather case though correct is almost certainly a period replacement of exactly the correct type. It is likely therefore that the instrument was sent for repair and re-issue. This might account for the work done to the altitude ring which has at some time been re-silvered. In relation to date of manufacture, we can be fairly precise based upon the altitude range to about 9,000 feet.

Rare, eagerly sought after, and with compelling historical association, this WWI air altimeter is most definitely a collector’s lot.