Advance franking seal of office \"Imperial Director of post office German East Africa\" (Morogoro), two-line cancel \"franked / with 7 1/2 H. \" violet, with railway mail \"midland train ZUG 20 b 29.4.16\" to Dar es Salaam with arrival postmark, rare Indian letter, vertical archive fold, at the bottom opened, expertized Bothe and Jäschke Lantelme BPP