Aircraft strut psychrometer, with set and dry bulb mercury in glass Fahrenheit thermometers set in air tube to face direction of travel, made by Negretti & Zambra ( trade mark) and thermometers marked MO 31301/27 and MO 31302/27. Both also marked NPL 27. Dated 1927 Aircraft strut psychrometer 1927
Regnault's hygrometer (psychrometer) by Negretti and Zambra, 1 Hatton Garden, London, also marked 2279-I-1866, in fitted wooden case with pair of mercury-in-glass thermometers fitted with brass collars Regnault type hygrometer with mercury thermometer 1866
Psychrometer (wet and dry bulb hygrometer) in frame, with original cardboard packaging box (Casella Product No CE 013), by Casella (London) Ltd, UK, 1986. Wet and dry bulb hygrometer, British, 1986 1986