Nautical Sextant for RAF Flying Boat, 6B/177 1941 (SEXT50)
This is a WWII-era marine sextant from the UK, as used in the Patrol Bomber Short Sunderland.
According to collector George Fulford's notes:
This fourth and final one once belonged to the Cleveland Power Squadron No. 3. I bought it because of its very early date (1941) to see if there was any difference between it and the later models: there was none with the sextant itself though the wooden box has clasps for closing it rather than the sophisticated rotating wheels that came later.