This ingenious invention first patented in 1915 by Negretti & Zambra, is designed to accurately predict the weather in conjunction with wind direction and barometer readings, which are then set by two rotating discs, revealing a letter code corresponding to one of 26 forecasts printed on the reverse.

Not to be confused with modern replicas, this is a genuine period piece carrying the "Negretti & Zambra, London" name and patent number 6276/15. It dates to the 1920's, and comes complete with original instructions inside the N & Z branded cardboard box.

Measuring just 60mm in diameter and of ivorine construction, it's in good condition, boasting a historically reported accuracy of 90%.