Revenue stamps of Zanzibar
Zanzibar issued revenue stamps from when it was a British protectorate in 1892, to after when it became part of Tanzania in 1993. == Revenue (1892-1970) == Zanzibar's first revenues were Indian revenue or special adhesive stamps overprinted ZANZIBAR in capitals, and these were issued between May 1892 and August 1894.
Source: Wikipedia — Revenue stamps of Zanzibar (CC BY-SA 4.0)