I recently saw a program aired on PBS called The American Flag: Two Centuries of Concord & Conflict. In this program they mentioned that 2 previously unknown American regimental flags from the Rev War had been placed for sale at Sotheby's by the family of a British general who had defeated the American forces. They had been displayed in their home in England and were sold for, I believe 3.1 million $.

There is a video available from the FlagCenter.org