A very rare Astens Patent No 2853 aneroid pocket barometer altimeter No 30 c1907

Pocket barometer having 1⅞” silvered and engine divided dial, the outer crown-operated altitude scale calibrated in feet with a range from 0 – 4,000ft divided down to 50ft, the upper part marked “Astens Patent No 2853, 1907,” and serial no. “30,” the lower part with inset or subsidiary dial marked Ascent and Descent with a range of 100ft divided down to 5ft. Fine blued steel pointers under bevelled glass.

The movement driven from a single 1” capsule, the signal transmitted via a fine chain to the central arbor and thence by an attached large six-spoked fine gear to a pinion set in jewelled bearings supporting subsidiary pointer.

All contained within a semi barrel form case, engine turned finishers, calibration port to verso, extension post and bow.

Presented in its original burgundy leather over timber, green silk and velvet lined case. Snap closure on a button release.

Condition: Fully serviced, conserved, and calibrated under laboratory conditions, the movement working well across the range. The dial crisp and clean, the case verso with some abrasions and wear, otherwise retaining much of its original lacquered finish. The crown-operated altitude scale moving freely with precision. The travel case structurally sound, externally faded with ware and minor losses. The fabric interior with fading to lid silk, the lower case velvet with good colour.

Comments: This is the only recorded example of the Patent No. 2853 of 1907 of Joseph Charles Asten. His claims, he seems to accept, come very close to those of John Thomas Daniels, Patent No. 2457 of 1889, and in certain respects it is difficult to see how this patent was granted. Both instruments rely on high gearing to achieve greater resolution, the mechanical arrangements bearing a remarkable similarity.

In any event, this is a very important development in the aneroid system. However, owing to the issues of initial inaccuracy further magnified through gearing which only served to further diminish accuracy through friction, it was likely a failure commercially. Quite apart from the shortcomings endemic within the design, the additional costs of construction would certainly have placed this in the market as a very expensive item. These factors clearly explain the rarity of this instrument and point to its clear lack of commercial success.

Interestingly, this instrument is of a markedly different internal design to that cited in the patent. It may be that, as examples were produced, different arrangements were trialled and that this was really one of a series of prototypes.

One thing is certain – making here is of the highest order more akin to fine watch making. The quality is very high and though clearly not made by Asten it was doubtless made under his supervision and on his commission Of the makers at that time capable of turning out quality of this type very few spring to mind, but it may perhaps be the work of J.H. Steward. Numbers manufactured would have been minimal – perhaps a few dozen.