My father has an old pistol in NJ. He's had it under his bed for 40 years and forgot all about it. A little while ago he dug it out and I'm interested in restoring it. It was given to him by his father and there is no paperwork on it. It likely was brought back from WWII Germany, but we don't know for sure. Since it legally doesn't exist does he have to have it registered? Does he have to have an FID to own it? If we wanted to take it to a range or a gun smith I don't want to run into any possible legal trouble. I don't even know where to begin to look for answers.

Welcome to the forum! He is not required to register it, since handgun registration in NJ is VOLUNTARY. If he inherited it, he got the gun legally and can keep it in his house legally. If you bring it to a gunsmith in NJ you may have a problem getting it back from the gunsmith without an FID card. He should get an FID card since he will need it to buy ammo anyway in NJ, and this will make proving he is eligible to own a gun easier should he need to prove this at some point.

No permit is needed to own it. He may legally take it to the range. He will however need a FPID to acquire ammo.