True Wind Indicator made of metal, possibly anodised aluminium. A rectangular frame carries a rotatable inset circular scale 112 mm in diameter, reading 0–180 (black)–0 (red) with radial slot labelled 'Wind you feel', scaled 0–90 with a slider controlled from reverse side. The rectangular frame carries a scale on the right-hand edge, labelled 'Wind ahead 90–0 Wind astern 0–70'. On the left-hand upper corner, a slot carries a locking lever labelled 'Ship’s speed'. On the right-hand corner is a locking lever labelled 'Wind' and 'Wind astern'. At the bottom is the notation 'SRE'. The rear is labelled 'Ship’s Course', 'S.A. Ltd London' and 'Serial number A 89190'. It also has a circular scale 0–360 degrees with a radial slot marked 0 -60 with sliding knob and locking knob, labelled 'True Wind Knots'.

The True Wind Indicator was designed primarily to help solve wind-finding prolems for launching an aircraft from a ship by catapult (assisted take off gear). It allowed the operator to work out the 'true wind' based on the apparent wind and the ship's speed and heading. By setting the dials and scales on the front of the instrument to the ship's speed and heading and the force and direction of the apparent wind, the scales on the back indicated the speed and heading of the true wind. The True Wind Calculator could also be used for meteorological purposes and gunnery. The instrument has a wooden box.