A very good, scarce, pigskin cased aneroid barometer and easel forecaster made to special order by Negretti & Zambra, No 20996, c1925

Negretti & Zambra Forecasting Aneroid No 20996 c1925


Forecasting Aneroid barometer having die-struck dial with barometric range from 28 – 31 inches of mercury, divided to 1/20ths of an inch, the upper portion marked “Forecasting Aneroid,” the lower “Compensated,” signed by the maker “Negretti & Zambra, London” with “N&Z” logogram, serial no. “20996.” Fine blued steel pointer set beneath bevelled glass retained in a rotating bezel with index. First quality lacquered brass movement of conventional pattern set on a gilt chassis and driven by a single 2″ capsule. Type two drum form case, the circumference marked with altitude correction scale from sea level to 3,000 feet, altitude index locked to position at crown.

4¾” lacquered brass forecaster of tri-concentric design, having 1st pattern swinging easel type stand. Signed by the maker “Negretti & Zambra,” with patent date 1915. The whole contained within a pigskin over timber green velvet-lined case with separation squab, snap closure and button release.

Condition: The subject of a complete re-build and calibration under laboratory conditions, see performance chart below. The barometer, very clean crisp dial, the glass with minor abrasions, one very minor chip. The brass case retaining a very high proportion of its original lacquered finish with some losses to bezel and verso. Working well with a much better than average degree of accuracy, good progression and very sensitive. Both bezel with index and altitude correction move fully and smoothly. Locking crown operation works correctly.

The forecaster in good overall condition, all functions operating smoothly. It retains most of its original japanned and lacquered finish with minor abrasions only.

The case in remarkably good condition – most are very dilapidated. The pigskin covering with signs of age, minor marks and very slight abrasions. Some minor damage to one corner which has been re-glued, the entire case is structurally sound. The green velvet interior, vibrant with excellent colour, some signs of shrinkage to formers.

Comments: Of the many instruments Negretti & Zambra produced, two stand out: the Weather Watch and this, its big brother, the Forecasting Aneroid, essentially a much more user friendly version of the Weather Watch, made in significantly smaller numbers as a special order item only. Negretti & Zambra spent around 10 years developing the forecaster, and, if used correctly, it can be around 80% accurate.

Altitude correction is achieved by turning the crown anti-clockwise – the entire back of the instrument including the movement may then be rotated. Arranged around the circumference of the instrument is an altitude scale – as the back is rotated a large black triangle located on the circumference of the back may be aligned with the altitude of the position from which observations are made. This reduces all readings to sea level. A maximum station height of 3,000 ft may be set.

Image of Negretti & Zambra Brass Forecaster & Weather Aneroid Instructions

(Leaflet in Vavasseur Antiques Archive)

This particular instrument is of particular interest, the barometer is set in the deeper (type 2) case, the dial very unusually has a return around its circumference resembling the lid of a jam jar, it is altogether of heavier construction. The inside back and movement all marked with assembly number ‘6.’ Generally this appears to be a higher quality instrument than others that I have examined, this is consistent with Negretti & Zimbra’s “sweet spot” in making, a period loosely defined as lying between 1895 and 1928.

Generally, this is one of those “Rolex” factor instruments – it combines fine aesthetics with quality, rarity and that gadget appeal. In the round a very good and extremely collectable piece.

Dimensions: 5½” wide x 6″ deep x 2¾” high

Stock No: CP1724

Price: £1450

 








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