Didn't Know This Was A Thing. Double Sided $1 Coins

Yes, Counterfeits exist for mule errors, most of which are made from altering genuine coins to make them look like a mule. The most common would be what are referred to as "magician coins," like that which is when two coins are essentially cut or ground down and then glued together to form a single coin which fool mainly novices. https://www.pcgs.com/news/mule-mint...s-the-rarest

This might be attempted because of the extreme value of the mule coins such as mentioned in that article. Although as a normal coin novelty I've always found them to be pretty neat. I also like some replica coins which would never be bought otherwise, but yes again there are scammers who might attempt to use such and somehow pass it off as the real thing to a novice. We saw alot of 1943 copper cents until they became so common everyone should know there are more likely fake when you find one.