I've had a C&R FFL for about 20 years and a CA COE for about 10 years. It wasn't so long ago that CA gun stores summarily disregarded their use or that C&R handguns that are Oly or C&R eligible need not be on the roster, however things have gotten better. Still, it pays to be prepared AND be nice about it when dealing with a store that may not be up to speed.

If you have a LGS that you've routinely used asking face to face, not over the phone, is best. Bring paperwork but be careful how you "educate". If you hit any resistance, may be best to not push it and go to another store. Or, leave the info, or let them figure it out on their own. Some folks like to believe they've decided on their own.

The LGS wants to make $$$, but they also know CA DOJ will sweat them if the make a mistake. Go easy, channel a little "Columbo" and it may help if you run into a little resistance.

As previously mentioned, C&R status is most often had by age however some guns are specifically listed as C&R in the ATF book. Demonstrating that the gun in question is of that model should be sufficient.