What does "U.P. Proof" mean? [решено]

I have this coin; it's most likely a restrike because it's proof, but the Numista page has two lines for the restrike; one with the comment "Proof; Restrike" and the other with "U.P. Proof; Restrike".

What does the second one mean?

Note sure what the letters mean, but look to the right of the date:

100 Korona 1907 U P

You're a genius, thanks!

I guess U.P. is probably the initials of a mint that made some of the restrikes.

My coin doesn't have the letters, so mystery solved.

imreh has the Hungarian catalogues and I suppose he would be able to tell us what the letters mean. It would be a good idea, then, to add that information to the Numista catalogue, as well as the location of the mark on the different coins where it is used (not always beside the date).

Utanvert Probaveret
The UP (Utanvert Probaveret) mintmark denotes that this is from the 1965 restrike issue.

Would it also be possible to find information on other later restrikes (without initials) of this coin, or were there too many over too long a period of time to do so?

Also thanks @Zac for confirming my theory.