Nice find,I just found this recently yesterday in a roll. Incomplete planchet on a war time cent a first for me.Most of the gunk came off with just my fingers.
The two sided aspect is really cool. I'm learning all about these and how much they are worth, as I've been going through an estate that I recently purchased. The fellow who collected the estate was apparently enamored with laminations, and had a bag with literally *300* of them, from dates between 1918 and 1970. Out of that lot, really only 4 or 5 were double-sided, as yours.
