British East Africa. (Zanzibar). 1931. envelope written from Nairobi addressed to Zanzibar bearing Kenya & Uganda 1, 1c brown (pair) and SG 78, 5c green tied by Nairobi/ Kenya date stamp, underpaid with circular 'T' hand-stamp and m/s '9c' bearing Zanzibar postage due SG D5, 9c black/orange applied and tied on arrival by Zanzibar date stamp. Very fine combination.