It seems like some "forger apprentices" has been practicing on this coin to turn a 1907 year into 1981. If you enlarge the picture, you see some strange metal melting signs and signs of waves around the year. [I think my English is not enough to properly define]
I suspect the Dimitrov workshop in Harmanli, Bulgaria
... they have a "good" track record of doing this with turning a common 5 Korona 1900 or 1908 into an ultra rare 1906 with same method. Check out the mintage:
https://en.numista.com/catalogue/pieces12866.html
Obviously, Mr. Dimitrov would not let the youngsters practice on a 5 Korona coin, as even a 1900 year is about EUR 50, so I bet this is the sandbox
btw, Mr. Dimitrov and team also does wonderful Roman denarii, a bunch of them is proudly exhibited in this topic:
https://en.numista.com/forum/topic16996.html
Imre