1887 7 Over 6 Proof

The 1887 7 Over 6 proof three-cent nickel has an unusual origin: apparently all of the 1887 three-cent nickel dies were overdated from 1886. Dies for each year were typically prepared at the end of the previous year, and the engraver working in late 1886 grabbed the old 1886 date punch out of habit, then realized the error and overpunched the 6 with a 7. Because multiple dies were affected, the 1887 overdate exists on every proof three-cent nickel for the year rather than being limited to a single die marriage.

The Mint attempted to clean up the error by grinding and polishing the dies to reduce the visibility of the underlying 6. The effort was hit-or-miss, which is why two distinct varieties emerged: the Weak Overdate (where the 6 is barely visible) and the Strong Overdate (where the 6 remains clearly prominent beneath the 7). Both varieties are recognized by major grading services. The 1887 7 Over 6 is one of only a few overdated proofs in US coinage history, which gives it collector interest beyond the usual variety premium.