Cal. Code Regs. tit. 13 § 635
Markings on the housing of an aftermarket lamp or reflective device shall be externally marked on the shell or other fixed part of the housing or shall be readily visible through the lens. Required markings may be placed on the door, grommet, bezel, or ornamental ring provided such part is so shaped or indexed to preclude its being installed on a housing of a different make or model. When removal of the lens from the housing would destroy the device, the housing is not required to be marked if the lens markings differ from those on any previously manufactured lens. External housing markings are not required on lamps which are packaged for sale in a disassembled condition and are marked so that the housing markings are visible when the lamp is installed on a vehicle and the lens is removed. Housings of separate control or power supply units (such as for reserve lighting and outage indicators or gaseous discharge warning lamps) shall be marked so as to be visible when the unit is installed on a vehicle.
Cal. Code Regs. Tit. 13, § 635
Note: Authority cited: Section 26103, Vehicle Code. Reference: Sections 24006 and 26103, Vehicle Code.