1951 mixed franking air mail cover from Austria to Cobourg, Ontario. Sent registered from Salzburg, Austria Sept. 4, 1951. Sender had applied a Canada Special Delivery label which the Austria post office crossed out & applied a registration label on top of. Sender put a Canada 10 cent special delivery stamp on the cover which was cancelled at the Montreal AMF post office to pay for special delivery service in Canada. Received in Cobourg Sept. 8th after travelling by train on the Montreal - Toronto RPO. Scarce special delivery cover.