Effective January 1, 2001, no handgun may be manufactured within California, imported into California for sale, lent, given, kept for sale, or offered/exposed for sale unless that handgun model has passed firing, safety, and drop tests and is certified for sale in California by the Department of Justice.
This query will return handgun models that are currently certified for sale in California.
Private party transfers, curio/relic handguns, certain single-action revolvers, and pawn/consignment returns are exempt from this requirement.
I copied that from the DoJ's site. A 1927 Argentine military 45 is a C&R pistol. There is no manufacturer to send samples to the gubment for testing. That is why it is excempt from testing!
Most gun shops don't really know what is going on here and I don't entirely blame them. However, according to the law it is entirely legal to do so. Depending on where you live I might be able to tell you where to go.