WW1 plain cover to Winnipeg Canada headed OAS (On Active Service) and cancelled with part Field Post Office 10.P datestamp JA 18. 

Censored with British Army type PASSED BY CENSOR 3201 cachet and counter signed 'A. P. MacKinnon' 

The censor would be Captain Andrew Pritchard MacKinnon serving with the CEF, an officer with the Canadian Army Medical Corps (DOB July 1880) enlisted March 16 and discharged July 19). 

Condition as shown

ID CA 29175