British WWI military mail in Egypt: 21 AP 1917 "honour" envelope from CAIRO to STROUD tied by CAIRO-I postmark in late usage to UK; backstamped next day APO SZ 10 (Cairo) transit; slit open at top, tear at top front. Unusual local routing from civilian to military post as most of the period military mail for abroad received by the civilian post office was not marked by a British military post office subsequent to overseas dispatch (although those marked like this generally originated from Cairo).