Mobile homes, commercial coaches, conversion vending units, medical units, recreational vehicles, and/or park trailers subject to the provisions of RCW 43.22.340 through 43.22.410, and mobile homes, commercial coaches, conversion vending units, medical units, recreational vehicles, and/or park trailers upon which alterations of body and frame design, construction or installations of plumbing, heating or electrical equipment referred to in RCW 43.22.360 are made after July 1, 1968, shall have affixed thereto such insigne of approval.