I wonder if there are any in circulation - I know the USMint has them in uncirculated form for insane amounts of money.
edit: Nope, all the American Eagle coins are just labelled because they needed something to label them. (Just called the Mint.) The highest denomination that's actually in circulation is the $1 gold coin. [It's not actually gold; it's just an alloy that looks gold.]
Though I think I got that you could actually spend the coins as currency, but it'd just be pretty stupid, since they're made of pure platinum, gold, and silver, so they're worth more than their denominations by a lot. ;)