Zanzibar. (Kenya). 1946. Envelope addressed to Zanzibar bearing Kenya/Tanganyika SG 134, 10c orange and brown (2) tied by Mombasa date stamp with 'Dead Letter Office/Zanzibar' receiver with instructional 'Addressed Insuffisant/Retour' and 'Inconnu/ Unknown' in violet and sent back to Kenya with 'Nairobi/R.L.O.' on reverse. Nice item of instructional mail.