Canada 1945 WWII Cover to POW at Stalag Luft III Germany Returned Home

Cover postmarked Barrie Mar 18 1945, to Canadian soldier W.O. Harry A. Long, imprisoned at Stalag Luft III (Lower Silesia), address crossed-out and handstamped ADDRESSEE RETURNED TO CANADA, manuscript "ex-POW REPAT" at bottom, with Field Post Office 539, MPO 304, Lachine MPO and Canadian Overseas Postal Depot RCAD Section Directory handstamp on back, exceptional condition for such well-traveled POW mail, scarce as such; Stalag Luft III was a Luftwaffe-run Prisoner of War Camp for captured Allied airmen. It was located in the town of Sagan, Lower Silesia (now Zagan, Poland). It was memorialized in the 1963 film "The Great Escape", which told the story of the dramatic 1944 escape conceived by R.A.F. Squadron Leader Robert Bushell.