Course and Speed Calculator Mk II Ref 6B/119 RAF 1939
This is an original WWII-era Course and Speed Calculator Mk II as used by aviators of the British RAF in its wooden case.
The case is marked as having been made for a different serial number, but the correct serial number has been painted on the outer end. The case measures ~ 11 in x 6 in x 2 in. It is in good condition given its age as the center rotates and slides along the base when the locking clamp is released.