TBF-1 Avenger Torpedo Bomber Cruising Calculator Mark 1-A, Ser # 4785-43 He-111 but the fluid in the

but the fluid in the rear chamber is absent and there is a slight internal rattle

indicative of a 1944 manufacturing date

as well as a close-up of an illustration from a B-25G technical manual

dated Oct 1943 revised July 1948

The C-13 Altimeter was used across all aircraft of the Air Corps US Army

TBF-1 Avenger Torpedo Bomber Cruising Calculator Mark 1-A, Ser # 4785-43 He-111 but the fluid in theThis is an authentic original WWII era Cruising Computer Mark 1 A designed specifically for the US Navy's Grumman Torpedo Bomber TBF 1. The purpose of the calculator was to determine the range, in nautical miles, of the aircraft under various conditions of aircraft weight, head tail winds, fuel quantity on board, true air speed, altitude, and throttle and supercharger blower settings. The calculator is essentially a custom 3 panel slide rule