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..
How on earth did you recall that thread, and how did you find it? I can't remember what I ate last night for dinner - although I am sure it was way too much! I am looking forward to finding out what that flag is. Cheers, Jim G.