registered?

Scenario…a guy buys a gun from a garage / estate sale or from some one that had it registered but no longer has a license to own firearms. No available info on the rifle as to was it or wasn’t it registered. what would the process be to find out if a firearm is registered or not. If it were registered how would you go about getting the registration changed? Is it even possible?
Thanks

cohod

The best thing you could do would be to look on the CFC website.