1949 cover sent internally with a 10c tied HONG KONG 6 SP 49. The postal authorities were unable to deliver the letter and various cachets were applied, including a large boxed ‘RETURN TO SENDER’, and boxed ‘RETOUR’ and’ NOT KNOWN’. A manuscript ‘Unknown’ and ‘PTO’ are on the front of the cover, the ‘PTO’ indicates the sender’s name on the back – The Mercantile Bank of India, Hong Kong. A RETURNED LETTER OFFICE HONG KONG 7 SP 49 datestamp is on the back. An appealing and interesting cover.