Readers Ask column from Jan. 18, 2016, issue of Coin World:

I found two coins while searching through rolls of coins and am not sure if they are doubled dies or errors. One coin is a 1937 Buffalo nickel and it looks as if it is a doubled die on the date. The other coin is a Memorial cent with what looks like a overstrike, but I am not sure. I would have thought such an overstrike would have damaged the coin so I am not sure.

Francis Ryan  /  via email

I forwarded your inquiry and images to Coin World columnist John Wexler, whose “Varieties Notebook” column is published in the third Coin World issue of every month. Here’s what John had to say:

“The Buffalo nickel doubling appears to be a common form of doubling known as mechanical doubling and not the product of a doubled die.

“This form of doubling has also been referred to as machine doubling, strike doubling, shelf doubling, and mechanical doubling.

“It is caused when loose parts in the coining press allow the dies to shift and/or bounce slightly at the moment of impact when the coin is being struck.

“On coins with raised design elements the result is a flat, shelf-like secondary image such as that seen on the date and left side of the long feather on your Buffalo nickel.

“Serious doubled die collectors view mechanical doubling as a form of damage to the coin rather than a collectible form of doubling.”

Concerning the 1990 Lincoln cent, Wexler believes the coin looks like it has been subjected to damage or alternation.

“I believe that what you see on this one is the result of another Lincoln, Memorial cent sitting partially across the obverse of your cent with the reverse of the upper coin face down,” according to Wexler. “The upper coin was then struck or squeezed into your coin, leaving a partial image of the reverse of the other coin on the obverse of your coin.

“I do not believe that this coin is a Mint error. Rather, as a damaged or altered coin, it would have no premium value.”