BAGUIO CAMP CIVILIAN INTERNEE TO UK
MANILA No. 1/PHILIPPINES, 1943 (Sep 25) clear duplex cancel on  Prisoner of War Post cover from female British civilian internee at Camp Holmes la Trinidad, Philippine Islands to Maidstone, Kent, England. Purple and red Japanese censor marks  and UK censor tape on reverse. This cover was probably transported on the  2nd voyage of M/V GRIPSHOLM and routed on to UK from USA. 
This type of POW envelope is in Garrett's book (p232), originating from Los Baños, postmarked as above and censored by "MAZAKI". This one has a different personal censor seal.

Although Garrett states that he has examined a few examples I believe that they are not that many. Personally, this is only the second time that I have seen this envelope. The first one in the late 1980s, shown to me by Mr. Rogelio de Jesus which he sold to an American collector. (eBay $535.00)