California Code, Business and Professions Code - BPC § 22411

No manufacturer shall sell any appliance in this state unless such appliance has been permanently marked with a serial number unique to that appliance. A marking that is required to be permanent shall be molded, die-stamped, or paint-stenciled or stamped or etched on metal that is permanently secured or indelibly stamped on pressure sensitive labels secured by adhesive that is adequate and suitable for permanent application.

Every manufacturer of an appliance to be sold within this state shall provide on the first page of the warranty or instruction manual, or on a separate card, a description of the appliance providing a space thereon for recording the model number and serial number, the description of the location of such numbers on the appliance, and instructions to the final purchaser of the appliance to record and retain such numbers.