Rev. Rul. 56-479

A supplier of ready-mixed concrete accomplishes the mixing of cement, sand, crushed stone, and water through the use of a large tank mounted on a truck chassis. The tank is set on gears and is rotated by a motor in order that the concrete may be mixed in transit. Held, since such concrete mixers are primarily designed and adapted for mixing concrete rather than as truck bodies, they are not subject to the manufacturers excise tax imposed by section 4061 of the Internal Revenue Code of 1954. However, automobile truck chassis on which these tanks are mounted are subject to the tax when sold by the manufacturer.