Seen one of these before & back then it wasn't answered either: WWII US Navy flag marked BRIT.U.S.
I will have have a look online but so far zip..
mike found this site on signal flags Signal Flags unfortunatly it isn't on their (got your hopes up then) googles not giving any answers (stupid monkeys) unless its commonwealth? or another flag altogether
Maybe its a British/U.S. Victory Flag!! LOL
Just a wild guess: Could it be the house flag for some shipping company?
Teutonicknights you might be close I saw a flag very similar to this during the summer on ebay and it had patches sewn all over it and the owner listed it as a war bond flag someone had made sewn a patch collection to. Unfortunatly I did not buy it because over the years someone had removed all the valuable patches and it was heavily mothed. However i do not remember if the color pattern was the same and I do not think that the V extended out to the edge like it does on this flag. Maybe it is a US coast guard flag of some sort?