Congrats Inix, Great find!
I don't know anything about furriers but this is one fine hat. Are you sure it's beaver? Looks like it could be something more exotic. Is it 7 1/4 by chance? LOL
You might research hat sizing info world wide. The white tag probably has the size on it. If any of those numbers can be correlated to a size in whatever standard other countries use it might be a hint where it came from.
Best wishes and good luck on an ID!