Here's what the California DOJ has to say:
SB 15 EXEMPT HANDGUNS
All curio/relic handguns as defined in Section 178.11 of Title 27 of the Code of Federal Regulations are exempt from the provisions of SB 15. Also exempt are single-action revolvers that have at least a five-cartridge capacity with a barrel length of not less than three inches, and that meet any of the following specifications:
1. Was originally manufactured prior to1900 and is a curio or relic, as defined in Section 178.11 of Title 27 of the Code of Federal Regulations;
2. Has an overall length measured parallel to the barrel of at least seven and one-half inches when the handle, frame or receiver, and barrel are assembled; or
3. Has an overall length measured parallel to the barrel of at least seven and one-half inches when the handle, frame or receiver, and barrel are assembled and that is currently approved for importation into the United States pursuant to the provisions of paragraph (3) of subsection (d) of Section 925 of Title 18 of the United States Code.
Additionally, Olympic pistols listed in PC section 12132(h)(2) are exempt from the provisions of SB 15. Consequently, firearms dealers, secondhand dealers, and pawn brokers may retain curio/relic handguns and/or firearms defined as Olympic pistols in their inventories for sales to the public.