cover 1893 (12 Apr.), 2a. registered envelope, size "F" with "REGISTERED LETTER" 62mm, no stops, used from Mombasa to Zanzibar, bearing ½a. dull brown and 2a. vermilion tied by "MOMBASA/A/AP 12/93" squared circle cancellations; envelope, roughly opened at right just affecting the 2a. adhesive, backstamped Mombasa and Zanzibar; 2½ annas postage and 2 annas registration