Rare Weather Watch Pocket Barometer by Negretti & Zambra No R/449 c1920 – SOLD
Weather watch pocket barometer with 2″ tri-concentric silvered dial, the outer section calibrated in inches of mercury with a range from 28″–31″, at 29½” marked “Sea Level,” the lower portion with settings for “Direction of Wind,” the inner rear dial with letter codes visible through three semi-curved rectangular windows cut into the centre forward dial positioned at 3, 6 and 9 o’clock, further marked with altitude correction scale “+/- 500FT,” “N&Z” monogram, “Patent 6276/15,” serial no. “R/449,” and signed in full by the maker “Negretti & Zambra.”
Fine blued-steel pointer set beneath bevelled glass. Rotating bezel, enabling setting of wind direction and causing interpretation codes to alter in the three windows. The case circumference with altitude correction scale from 0 – 3,000ft; rear section may be turned causing the whole movement to turn within the case, thus altering the position of the pointer relative to the dial. Verso of the case with compensation screw set at 7 o’clock and letter codes set to forecasts. The centre dial rotated via the crown. Suspension ring. The movement driven by a single capsule with bimetallic compensation.
The dial with a few minor losses, the crystal very good, the brass case retaining a proportion of its original lacquered finish. Crisp overall and functioning correctly in all respects.
The subject of a complete disassembly, appraisal of all parts, conservation and calibration under laboratory conditions. The instrument meeting strict conditions for performance and quality – see the performance chart below. It shows good sensitivity, smooth progression, and a very acceptable level of accuracy.
Working on these instruments illustrates their added complexity and the great care that is required to achieve proper function. The instruments were originally made to manufacturer’s tolerances and these can vary, requiring special attention in reassembly.
To use the weather watch, first note whether the barometric pressure is steady, rising or falling. Then set the station altitude using the circumferentially-marked scale and rotating the rear of the case aligning the index point the correct station height. Note the direction of wind by rotating the bezel so that the arrow for wind aligns with the correct compass cardinals. Finally, read from the window marked “Fall” “Steady” or “Rise” as appropriate – the letter shown can be then related to the forecaster messages on the rear of the pocket barometer.
Marketed as an especially sensitive aneroid barometer, the movement was manufactured to provide a greater degree of accuracy than standard. At the point of purchase, this was a substantially more expensive instrument than standard pocket barometers.
These instruments are seldom seen and have achieved a near cult status amongst collectors. Certainly produced as early as 1915 and probably remaining in production into the 1930s, modest numbers were produced.
There is no doubt as to the collectability of this fascinating weather watch.
NB: The image of the Directions for Use is of an original document held in our Archive – a copy will be provided with this instrument.
Dimensions: 2⅛” wide x ¾” high
Stock No: PB1375