Error collectors new to the hobby quickly encounter coins with unexpected bumps in the field and design. Expert Mike Diamond explains the most common types.

Horizontal die movements can cause the newly struck coin design to be repositioned, smeared, scraped or even completely erased.

Countries without a mint or in urgent need sometimes outsource coinage. Hired mints can make errors, too, including weak hubbing. What is that, exactly?

The hammer die is ordinarily locked into its assembly by a clamp. But any locking mechanism can come loose or break, allowing the die to shift to one side.

When foreign matter ends up embedded in a coin, one expects the embedded matter to take and hold an image when struck. There are exceptions.

If dies are updated by punching some or all of the digits of the date into each working die by hand, possibilities for error are endless.

Edge designs are often added in a separate step from the obverse and reverse minting. Errors are apparent in several examples.

Diagnosis is best with more than one example, especially of an unfamiliar error, like the 1987 Indian 5-paise coin shown March 14, with an irregular outgrowth.

Many die cracks extend in from the edge of the die and end blindly somewhere in the field and design.

There are any number of reasons to modify a coin’s design. It might be done to improve the strike or reduce wear in particularly vulnerable areas.