Rare WWI Pilot's Wrist Air Altimeter by Becker No 320 c.1916

Rare early lacquered brass Ww1 wrist air altimeter Aid No 320 by F.E. Becker & Co, Successors W&J George Ltd 1897, Hatton Wall, London c1916. Air altimeter having 2¼” silvered die struck stepped dial, the outer bezel operated altitude ring calibrated in feet with a range from 0 – 10,000ft and divided to 100ft increments, stations marked in red and annotated “Feet.” The inner part with barometric scale calibrated from 22–31” of mercury, divided to 10ths. The upper part marked “Compensated,” the lower with maker’s name and address, “F.E. Becker & Co, Successors, W & J. George Ltd 1897, Hatton Wall, London.” Blued steel pointer. 1.065” single nickel alloy capsule driving a conventional C spring tensioned movement, bimetallic compensation, all raised over a circular lacquered and grained brass chassis. All contained in a heavy duty drum form case, the verso with scratched annotation  “Aid 320” and dated “21/V/16,” later leather strap of correct pattern. Comments:- A really lovely example of this very hard to find instrument, perhaps the most refined of the standard Vidie pattern units as adapted for air altimeters. Particularly interesting as dated 1916 and marked by the Aeronautical Inspectorate Department (Aid) as no. 320. Very much a collector’s piece.