Pocket barometer having 2½” silvered and die struck dial, finely divided scales, the outer marked “Feet” with a range from 0 – 3,000ft and divided down to 10ft increments, the inner barometric scale marked “Inches” of Hg with a range from 27.5 to 31, further divided 100^th”. The upper part marked “Compensated.” Fine blued steel pointer, reflector ring with crown operated index, bevelled glass.

First quality conventional 1⅛” capsule driven movement tensioned on a C spring, the chassis initialled “4 JS” and the cock with finisher’s initials “WB” and dated “12/01/09,” all contained within a barrel form case with ribbed circumferential decoration, the verso with calibration port, movement chassis mounting screws.

The whole within its original brown leather over timber, silk and velvet lined case, snap closure on a button release.

Condition: This instrument has been the subject of full conservation, servicing and calibration under laboratory conditions, see performance chart. Overall crisp, the dial excellent with little sign of ageing, pin point marks only. The glass clean and chip free. The aluminium case with general hazing, very fine abrasions and some scratches, small barely noticeable depressions at the 4 o’clock position. The instrument responds well to pressure change with good sensitivity and stepless progression, acceptable levels of accuracy. The index mechanism operates well with precision. The travel case structurally sound, worn and discoloured externally with some losses notably to lid edge. The internal fabric worn, though with essentially good colour. Signs of historic repair to hinge.

Comments: This is a rare instrument, particularly given its size. Construction in aluminium at this time drew a premium price and most probably was supplied by special order. The index mechanism operated from the crown with attached index to reflector ring is very unusual.

A very attractive instrument, and certainly a piece for the collector or connoisseur alike.

Short & Mason was founded in 1873 by Thomas Watling Short and William James Mason in London. Makers of precision measuring instruments including barometers and compasses, they became leaders in the design of barographs and aviation instruments in the first quarter of the 20th century.