Cal. Code Regs. tit. 19 § 987.4
Before reproduction of the Seal of Registration, there shall be inserted in the box at the bottom of the reproduction, the registration number assigned by the State Fire Marshal to designate the category of the licensee. The category shall be designated by the capital letter proceeding the registration number as follows: "M" for manufacturing, "I/E" for importer/exporter, "W" for wholesaler. The designation for model rockets and signaling devices shall be as follows: "MR" for model rockets, "HPR" for high-power rocket motors, "L" for land signaling devices, "S" for sea signaling devices and "A" for air signaling devices. Signaling devices intended for more than one function shall use all of the appropriate letters.
Cal. Code Regs. Tit. 19, § 987.4
Note: Authority cited: Section 12552, Health and Safety Code. Reference: Sections 12502 and 12618, Health and Safety Code.