Have you found an official presidential standard with fringe at auction or private sale?

Official flags of the president and vice president are a rarity in any size, but they do appear on the market from time to time mostly as automobile flags. Very rarely is an office flag with fringe offered at auction or private sale, yet about 3 years ago at an auction in New England a Bill Clinton office presidential standard was auctioned for about $45,000, a highest price every paid for a presidential flag up to that time. Have you seen official presidential office flags for sale? Do you know how to authenticate an official flag if you saw one?