A very good scarce pocket barometer altimeter with loupe by Naudet, France, c1880

Pocket barometer having 1¾” diameter die struck silvered dial with return, calibrated in cmHg with a range from 60cm – 79cm divided to 1mm, inner altimetric scale calibrated in metres, annotated “Hectomètres,” with a range from 0 – 2400m divided to 10m. Blued steel pointer, bevelled glass with cemented loupe, index below, the assembly positioned on the dial on a rotating bezel.

Typical C19th Naudet movement driven from a a single 1¼” capsule and tensioned on a C spring, set on a primary steel chassis with brass sub chassis supporting the cock, fine gain adjustment. Assembled within a banded semi barrel form case, the verso struck with PHNB (Naudet) logogram, calibration port. Extension post with suspension ring.

All contained within its original fine brown leather over timber, green silk and velvet lined case, snap closure on a button release, the lower case with original paper instruction sheet entitled “Baromètre, Holostérique, Orométrique, par Naudet et Cie.”

Condition: The subject of a full service, restoration, and conservation. The movement working well with acceptable accuracy across the standard range, see performance chart. Generally good condition, the dial with some ageing, the case retaining a good proportion of its original finish. The leather case sound with good colour, the fabric interior retaining much of its original colour and vibrancy. The paper instruction sheet aged with pencil annotations.

Comments: An unusual instrument noteworthy for its overall condition and completeness. The instruction sheets are extremely rare. This particular instrument designated “Orométrique” is unusual as the majority from this maker are defined as “Altimétrique”. It will be noted the instruction sheet carries the same descriptor, and this barometer altimeter appears in Naudet’s catalogue of 1891 with the “loupe sur le verre” as an optional extra.

An orometer is a barometer that has a secondary altimetric scale, an altimeter is a barometer that has an altimetric main scale.

A very unusual and collectable instrument.