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
Well, then Mr.Dimitrov is exempted from prosecution
However, if you look at the enlarged picture of the date, you can see that the figure 8 is mispositioned, and the last figure 1 is different from the first one. So, it shows, that if the individual coin was not altered, then the mint used some of the original 1907 dies and altered it to 1981 ... and yes, it is not a very high quality engraver work. That is what you call ugly, Arno