Rare Weather Watch by Negretti & Zambra No R/3219 c.1924

A good gilt lacquered brass weather watch aneroid pocket barometer forecast prognosticator No R/3219 by Negretti & Zambra, London, c1924. Weather watch pocket barometer having three piece silvered and die struck dial, the upper and outer part calibrated in inches of mercury with a standard barometric range from 28” – 31” and divided to 1/10th”, the lower outer part with wind directions on the compass points, bezel operated setting at “Direction of Wind.” The inner part, rotated from the crown, with short altitude compensation scale to top, three apertures for falling, rising and steady pressure revealing the Arabic letter codes, “N&Z logogram,” “Patent 6276/15,” serial no. “R/3219,” and signed by the maker at lower part. Blued steel pointer, bevelled glass. Conventional 1st quality Vidie pattern movement driven from a single 1” nickel alloy capsule tensioned on a C spring, contained in a semi drum form case, altitude correction scale to circumference, circular interpretation guide, and calibration port to verso. Altogether with its correct leather over timber, green velvet lined case with a further circular celluloid interpretation guide to inner lid. Snap closure on a button release. Gold block initials “Aej” to lid. Condition: The subject of a full service, conservation and calibration under laboratory conditions. The movement working well with excellent sensitivity and progression, and very commendable accuracy - see attached performance chart from dynamic test.  The dial with clear signs of ageing, some losses and minor abrasion. The case retaining virtually all its original lacquer finish, remaining bright and vibrant. Very minor loss to extreme edge of bezel. All adjustments working freely with just sufficient inherent resistance to prevent accidental alteration of settings. The leather case the subject of some conservation, including a replacement release button and leather over, small section leather inside lid adjacent to hinge. Historic repair to hinge which appears sound. A slight mismatch between top and bottom of case. Comments: This is the Rolex of the pocket barometer world, probably the single most sought after and iconic instrument of this type. Certainly the had-to-have device of the day though the price probably restricted the market somewhat which might explain the very few that are seen to-day. These instruments were developed from meteorological data collected over 13 years - N&Z claimed around 80% success in an accurate forecast, if the instrument operated correctly. This is a good example, complete in all respects and in very original condition. Certainly highly collectable. Nb: The original instructions shown are in the Vavasseur Archive - a copy will be provided with this instrument. How a Weather Watch Works: You will need to observe the barometer over a few hours to determine rising or falling pressure or if it remains steady. You will need to know the wind direction and the season. Operation is simplicity itself: 1. Set the wind direction by rotating the bezel aligning the small black arrow with the correct compass point 2. Rotate the crown causing the centre upper dial zero point on the semi-circular altitude scale to align with the barometer pointer 3. Read from one of three viewing ports relevant to season, S-Summer/ W-Winter, and pressure condition, Rising, Falling or Steady 4. Refer to interpretation disc in case lid or verso of instrument, the letter denoting one of 26 different prognostications