A scarce and very fine precision ship’s bulkhead aneroid barometer no. 553 manufactured January 1969 by Yanagi Gauge & Instrument Mfg. Co. Ltd.

Marine barometer having aluminium dial with parallax mirror, the twin barometric scales in millibars and millimetres Hg, having ranges 920 – 140 mbar divided to 0.5 mbar and 690 – 780 mmHg divided to 0.5 mmHg respectively. Marked to the top “Aneroid Barometer,” the lower part “Compensated Temperature and Acceleration,” Yanagi Keiki “yk” logogram, serial “No 553,” “Date 1969-1,” and signed “Yanagi Gauge & Instrument Mfg. Co. Ltd..” to bottom. Fine japanned alloy pointer, flat glass with centre mounted gilt brass index, chromium plated wheel.

Constructed principally in non-ferrous alloy, the mechanism driven from two horizontally opposed tryptic and autonomous 50mm diameter pressure sensing capsules, each capsule set with spring steel actuating extensions acting in opposition about a finely pivoted bar and common fulcrum, terminating at one end with an adjustable counter weight, the other with fine adjustment and connecting bar to rack assembly. Finely pivoted at top and bottom with base mounted return hair spring, finely set horseshoe gain adjustment, counterbalanced rack driving a jewelled pivoted arbor with driven pinion, maintained at its base by a dial mounted cock on twin standoffs.

All maintained within a substantial cast and machined chassis with top plate. The dial maintained on two pins with coil spring tensioning operating within short curved slots in the top plate enabling rotation relative to the movement, adjustment made via a shaft, on opposing ends a slotted head visible on instrument verso, on the other a pinion acting on an 80mm diameter gear fixed at the dial centre. The whole suspended from the back plate at three points on coil springs, the circumference with coarse thread to receive case tube and glass, and contained within a heavy drum form case.

Condition: The subject of a full service, conservation, and calibration under laboratory conditions. The movement clean and highly sensitive.

The dial about fine, the case retaining most of its original green painted finish.

Comments: These instruments are very hard to find in the UK and Europe. Most were sold to Far Eastern shipping companies and armed forces of those nations.

This is by no means a mainstream barometer, the essence, employment of single or groups of pressure sensing cells reserved for only the highest order mechanisms. This instrument is able to resolve pressure fluctuation of 0.1 mbar or 0.075 mmHg.

The design defines the pinnacle of development of the aneroid barometer.