Mining barometer having inverted 2⅜” silvered and engraved dial, outer crown-activated altimetric scale calibrated in feet with a range from -2000ft to 4000ft, three scales divided to 20ft, 50ft and 100ft. Impressed “Regd No 149175.” Inner barometric scale with a range from 27” – 33” inches of mercury, divided 1/20^”. The presenting upper part marked “Ascent” and “Descent,” and “Compensated,” the lower part signed by the retailer “Page, Keen & Page, Plymouth.” Blued steel pointer under bevelled glass. Conventional single capsule movement tensioned on a C spring, dated

All contained within a nickel-plated barrel form brass case with calibration port to verso.

Condition: The subject of a full service, conservation and calibration under laboratory conditions, the movement working well to full scale with maximum error less than 1/10^th” across the scale, see performance chart. Dial very good clean and crisp with very minor marks only. The case retaining virtually all its original nickel plating, light scratches and abrasions.

Comments: A most unusual instrument of exacting quality., the geographical location of the retailer would strongly suggest the application being tin mining. Reinforcing this is the way in which the dial is divided, giving the accent to use as an altimeter, ie determining depth of the mine as well as prevailing barometric pressure, two important considerations for general safety from the ingress of noxious and inflammable gasses from the rock strata. This instrument would almost certainly have been contained with a holder or protector, possibly affixed to a mine shaft lift cage.

Similar keyless action instruments are featured in the Francis Barker catalogues from 1909 and 1919 as Barker’s Improved Vernier Mining and Surveying Aneroid. The Registered Design No. 149175, issued to Francis Barker on 1 May 1890, refers to the scales on the dial.

A fine collector’s piece.