My Grandfather served in WW II, and brought home a Mauser pistol.

The markings on the side are as follows:

Mauser-Werke A.G. Oberndorf a. N.
Mod. H S c ======= Kal. 7.65mm



This gun has not been fired in probably fifty years.

Is it legal for me to have it, even though it's not registered and all of that?
Will I need to register it somehow?
I probably need to have it checked to see if it's safe before firing, but where would I take it?

I have a small amount of ammunition, so I can match to see if modern ammo will work.

Please help me out, thanks in advance.