(1) Each unit manufactured, sold or offered for sale in this state shall bear a legible manufacturer's identifying serial number which shall be prefaced by the letter "S". Each unit shall also bear a separate identification which shall include the date of manufacture and, where applicable, the plan review number. When the date of manufacture is coded, the bureau shall be informed of the method of coding.

(2) The manufacturer's identifying serial number and the bureau's insignia shall be permanently attached to the exterior wall adjacent to the rear or side exit.