The port city of Aden (now part of Yemen) used the stamp of India until 1937, when the colony released it's own stamps. The fist series, released 1 April 1937, feature a Dhow, an indigenous fishing boat.
The second set was released 19 Jan 1939. With the same border and portrait of His Majesty, the series showed scenes of the colony. Here is the 1 anna value showing the Port Harbour:

A third set issued on 1 October 1951, was the second set overprinted in cents & shillings (British East African Currency).
Most of the mail from Aden is from the British military garrisoned there. There are lots of postmarks reading "ADEN CAMP" for those in the army. These are the difficult ones... the early and later Royal Air Force Post Office:

This is the 1˝ anna value from the second series.

This is the difficult "R.A.F. 11" postmark.
Check your stamps!
David