kerrison predictor sight

A telescope elevation sight as used on Kerrison Predictors for anti-aircraft fire.  Predictors were used to aid the accurate firing of the large number of anti-aircraft guns that were deployed to defend the home front during World War 2. Each was fitted with two sights, one for bearing and the other for elevation.  Operators would sight and track an aircraft through these scopes, and the predictor would help set the gun to take into account the altitude and speed of the enemy aircraft and time it would take for the shell to reach its target.  This particular device, an elevation scope, was made Cooke Troughton and Simms. It survives in near mint (possibly unissued) condition and is contained within its original box with associated labels.   NOT FOR SALE