US Coins

Market Analysis: Copper spots on classic U.S. gold coins

"Relatively tiny” copper spots speak to the originality of the MS-64 1926 American Independence Sesquicentennial quarter eagle, right, that brought $708, while a spotted 1891-CC Coronet gold eagle in MS-61, left, sold for $3,068.

All images courtesy of Scotsman Coin & Jewelry.

Classic era U.S. gold coins are struck on planchets that contain 90% gold and 10% copper.

An improper mix of this alloy results in occasional copper spots seen on struck coins. These spots provide character to a coin and are a product of the minting process, though some collectors prefer coins without spots.

A 1926 American Independence Sesquicentennial commemorative $2.50 quarter eagle graded Mint State 64 by Professional Coin Grading Service has a few spots on the obverse and reverse and realized $708, with bidders responding to the nice luster in Scotsman Coin and Jewelry’s July 22 auction.

Scotsman also offered an 1891-CC Coronet gold $10 eagle graded MS-61 by PCGS that brought $3,068. The cataloger wrote on the better-date Carson City Mint issue, “Carefully detailed and somewhat lustrous, the surface shows evidence of some kind of curious greyish haziness,” adding, “Quite a number of copper spots show throughout, most of them relatively tiny.”

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