This is a British Turn and Slip gauge of the 1950s of the type fitted to the Gloster Javelin RAF fighter jet. This item appears to be in serviceable condition and has a two pin connection.

A Turn and Slip gauge indicates to the pilot the direction of the turn, the steepness, and whether the aeroplane is making a clean turn or is slipping sideways.

A Gloster Javelin

 This item is moderately rare.