In 1989, a Philadelphia man spent $4 on an ugly painting at a flea market, purely for the frame. Behind the painting he found something more valuable: a first printing of the Declaration of Independence. That copy sold at auction with Sotheby's for $2.42 million in 1991, and then in 2000 it sold at another Sotheby's auction for $8.14 million.
Given that the profitable find was one of 25 copies known at the time, out of a first edition printing of hundreds, it's easy to understand why there would be interest in finding the other copies. Several more have popped up, but most of that first edition, if they still exist, are out there waiting to be found.