One of the most unusual American gold coins is the Proof 1907-D $20. This first public appearance of this unique coin was in Sotheby's 1954 auction of the collection amassed by King Farouk of Egypt. Like many great rarities in that sale, it was lumped into a large lot with 33 other coins and, as might be expected, it received little attention. The coin appeared in subsequent auction sales in 1959 and 1960, then disappeared from the market until 2001, when it reappeared in a Stack's sale and sold for $34,500. Since then, it has risen steadily in price until it sold for "over $500,000" in a private transaction circa 2014-2015. In March 2016, Lee Minshull of Minshull Trading offered the coin for $295,000.
No documentation exists to explain why this coin was made, but it may have been struck as a souvenir of one of the last coinages of the Denver Mint. The characteristics of this coin are nearly identical to those of Philadelphia Mint Proofs: full strike, highly reflective surfaces, and the presence of lintmarks (caused by tiny threads from a polishing cloth). It's appearance is markedly different from that of any of the 1907-D Double Eagles made for circulation.