In my small collection i have this 20 Italian centimes, 1918. Looking more closely i noticed it's overstruck on a 1894 20 Italian centimes coin. The first is the 1894 coin, the second is the 1918 one:
I can see the 20 on the coin, but if the 1918 was struck over an 1894 then why is part of the 20 from the 1st strike on top of the 2nd strike?
this is not really an error, Krause lists the 1918 coin as "overstruck on KM28" which is the 1894 coin. I do not know why this was done, and I assume all 3 years they made this design (1918,19,20) was all overstruck.