Reciprocal die deformation is a rare phenomenon in which one die face sinks in while the other bulges out in a complementary fashion.

Pre-strike planchet damage is infinitely variable in its severity, extent, location, and appearance.

Elongate cuds may result from brittle die failure, examination of the coins suggests.

Collectors' Clearinghouse column: Israeli coins show variable form of raised rings just inside design rim.

The far end of the damage spectrum for coining dies is occupied by rare and often singular cases of catastrophic die damage.

A novel form of design duplication from grease-filled dies on copper-plated zinc cents is still poorly understood.

Freshly minted coins are sometimes adorned by parallel stripes. The physical characteristics point to diverse etiologies, which are often poorly understood.

The D Mint mark on 1987-D Lincoln cents is about as large as they come on Lincoln cents. Several examples truly stand out.

On Aug. 18, 2014, Daniel Lucak posted photos of a 1998-P Kennedy half dollar with a black nodule embedded in the coin’s edge on the Coin Community Forum.

Stain on 2014 gold Kennedy half dollar likely from oil on the die or blank not a frosting error.