The biggest issue is that there are the laws for firearm sales/transfers in 49 states, and then there's Cali. The California DOJ regulates firearm sales in their state and the laws are much more restrictive than in the others. Any handgun transfer requires FFL intervention in all states, so it's very likely that even though the gun is quite dated as you say, it'll require intervention of a licensed dealer. If the gun is 50 years old, as I believe you said, it puts it as a 1960s vintage and this doesn't fall under C&R guidelines. Even if it's from the '50s, it's pretty unlikely that you can do an FTF sale without involving a dealer and paperwork. Being able to vouch for the character of the buyer is pretty much a moot point, whether you agree with this or not.