1878 $20, CAM (Proof)

With an original mintage of only 20 Proofs, the 1878 Double Eagle is automatically a great rarity in Proof condition. However, it is an even greater rarity because of attrition over the years, resulting in only 8 to 10 examples known. Of the known examples, at least one is a circulated Proof and another is PR62. The best example is believed to be the Superb Proof from the Eliasberg Collection, described as "Gem Brilliant Proof-67" in 1982. The PCGS Auction Prices Realized listing shows 12 listings, but some are reappearances of the same coin, resulting in only seven different examples. To these can be added an example in the Smithsonian Institution, plus one or two from old auctions that could possible be additional examples. Under today's grading standards, most of the known examples would be Cameo or Deep Cameo.