The following is the Collectors' Clearinghouse column from the Aug. 15, 2016, issue of Coin World:

The hammer die is designed to move vertically during its downstroke (which culminates in the strike) and during its retraction phase. Horizontal movements are undesirable and can leave behind a host of errors. 

Horizontal movements can occur before impact, during impact, and during retraction. If a lateral shift occurs during impact or early in retraction (before it’s cleared the coin’s surface), the die will drag itself across the coin. This will cause the newly struck design to be repositioned, smeared, scraped or erased. Effects will also vary depending on whether the movement occurs in the course of a single strike or during a second strike.

A skidding die can shift to one side as it’s being driven into the planchet. This effect can be seen on two 1999-D Jefferson 5-cent coins struck in-collar by the same wildly oscillating hammer die. In each case the hammer die was well-centered when it first contacted the planchet. 

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As it sank deeper into the planchet it shifted to the left side in one example and the right side in the other. This movement left behind a featureless crescent that separates the edge of the coin from the edge of the field portion of the design. Transverse (crosswise) striations found in this zone testify to the die’s destructive movement. While this error resembles a horizontal misalignment, its dynamic nature warrants a distinctive name. 

I’d previously grouped such errors with design ablation errors, but a more apt term would be a “skidding” or “sliding misalignment.” Henceforth, “design ablation error” will refer to cases in which the design is scraped off during a second strike.

In both 5-cent coins the hammer die shifted back in the opposite direction after reaching the lowest point of its downstroke, smearing the newly-struck design. This smearing is considered a form of machine doubling called “slide doubling.”

Another effect of die skid can be seen on the obverse face of double-struck 1976 Greetings token struck by the Israel Government Coins and Medals Corporation (Israel’s mint). The first strike was centered but weak. As the hammer die was lifting off the surface it shifted toward the southeast, scraping the Hebrew letters generated during the first strike. The hammer die descended again to deliver a second strike that was horizontally misaligned a whopping 50 percent and strongly tilted. The damage to the letters can be considered a partial design ablation error.

Die skid on the second strike can completely erase a newly-struck design as seen in the quadruple-struck 2000-D Lincoln cent pictured, first discussed in a column that appeared in the Sept. 13, 2010, issue. Here the reverse die functioned as the hammer die. After a normal first strike, the coin received a 73 percent off-center uniface strike at the northern end of the reverse face, with the hammer die making direct contact with the coin. After initial light contact, the hammer die shifted a considerable distance northward, completely removing STATES OF AM and E PLURIBUS UNUM. The final two strikes were delivered in tandem (a saddle strike).