Popular are errors on dual-dated 1776-1976 coins that were struck to commemorate America’s Bicentennial.

Stack’s Bowers Galleries sold a 1976-D Washington quarter dime Aug. 19, which was an obverse den cap error. It was graded Mint State67 by Numismatic Guaranty Co. and sold for $2,880.

It was well-centered and measured almost 4 millimeters high. It was described as “This stunning Superb Gem obverse cap was created when the planchet entered the press before another struck coin was ejected.” The second step was to strike the planchet. It was then adhered to die for several strikes, sharpening and softening both the obverse and reverse impressions.

A 1976-D Kennedy half-dollar obverse cap graded MS67 by NGC was sold for $3,600. The auctioneer wrote, “The reverse acquired the brockage of an previously struck Kennedy half-dollar, which is wide and distended, but shows a full face, part of IN GOD WE TRUST and even a rather sharp D minmark.”