Bob Kehn of Montana sent in a 1961 Franklin half dollar that is struck through grease and possibly other contaminants on the obverse and reverse.
Debris, (which can build up around machinery), made up of grease, oil, metal filings, etc., may work itself into and cover the dies. When this occurs it can fill certain areas of design and prevent those areas from being struck up on the coin.
On his coin we see that the entire word WE is missing due to the die being filled with Mint goop on the obverse while the “O” and portion of the “F” of OF are missing from the reverse.
While not considered a particularly major error when covering limited areas like this, on a Franklin half dollar, it is a welcome error that adds some moderate value to the coin.
As a general rule, this is a relatively common error type and in recent years it has become more of a nuisance than a collectible for minor examples as the Mint seems to be paying more attention to striking larger quantities of coins and less attention to cleaning up the dies today than when this Franklin half was struck.
In closing, I’d like to mention that I very often get inquiries in the mail that do not come with a self-addressed, stamped envelope (SASE). If you expect an answer to your inquiries, please make sure you include an SASE.
Ken Potter is the official attributer of world doubled dies for the Combined Organizations of Numismatic Error Collectors of America and for the National Collectors Association of Die Doubling. He also privately lists other collectible variety types on both U.S. and world coins in the Variety Coin Register. He is a regular columnist in Numismatic News’ sister publication, World Coin News, where he pens the Visiting Varieties column. More information on either of the clubs or how to get a coin listed in the Variety Coin Register may be obtained by sending a long self-addressed envelope with 60 cents postage to P.O. Box 760232, Lathrup Village, MI 48076, or by contacting him via e-mail at KPotter256@aol.com. An educational image gallery may be viewed on his Web site at www.koinpro.com.