About the only way for you to find out the "status" of any given firearm would be to ask your local police.The problem, as mentioned, is that any problems crop up, and you wave buy-buy to that gun. The other pitfall/pratfall is of course, any gun you take to the police, they now have a record of.
Also, doesn't CA have some kind of hokey assault weapon ban? As I heard, the interpretation of the law is so convoluted that you can get documentation from the state that a weapon is legal and still be arrested and charged for possessing it. If you ended up with anything "interesting", you might just want to sit on it, or maybe move it quietly out of state.