Morocco agencies stamps had an overprint in the currency of the protectorate (French or Spanish). Mail posted with these stamps were transferred to the British post office agent for international carriage. If the mail was handed in at one of the British post offices, there was no need to overprint the stamps in Spanish or French currency as the mail entered the British postal system directly.
From 1937, ordinary British stamps were used on mail handed in at the British post offices. New issues during this period were used, but not overprinted "MOROCCO AGENCIES." Overprinted stamps, once again, were issued in 1949. They were only used at the post office in Tetuan. These may, primarily, have served a philatelic purpose.
The offices in the French zone had closed in January of 1938.
The British post offices in the international zone of Tangier used the same stamps as other offices. From 1927 until 1948, only stamps with the lowest face value (up to 2d) were overprinted "TANGIER." The higher values with "MOROCCO AGENCIES" were also used. These overprints did not stop in 1940. There were no British stamps issued between after the centenary of the postage stamp issue in 1940. The most used stamps of the current permanent series were printed in a paler shade. They were overprinted and used from 1944. The stamps were printed in pale shades to save ink and prevent wear of printing equipment. In 1949, the range of stamps was extended. Again, revenues from philatelic sales may have been a consideration.