Rev. Rul. 54-117

A low-bed trailer or semitrailer which is designed and constructed for transporting heavy equipment and which by special permission may operate on highways is considered to be an automobile truck trailer or semitrailer within the meaning of section 3403(a) of the Internal Revenue Code. Sales of such trailers by the manufacturer are subject to tax under that section even though they may exceed the maximum width and weight limitations prescribed by the laws of the various States.