1958 D Wheat Penny Overdate

Great idea on the acetone.

I would have to say I agree that the mint absolutely wouldn't have working hub dies from two separate years (1956 & 1958) in the hubbing machinery at the same time.

MD can definitely give you an "Echo" effect that might be mistaken for a second number, especially with gunk interfering with a clear view. That MD "Echo" shows up well on the 195. The acetone bath should remove the gunk around the date.