Rev. Rul. 57-301

Preformed coils of the type used in armatures for automobile generators are not themselves considered automobile parts or accessories within the meaning of section 4061 of the Internal Revenue Code of 1954, and separate sales of such coils are not subject to the manufacturers excise tax imposed by that section. However, the insertion of preformed coils in used armatures for sale is a `rebuilding' operation. Accordingly, a rebuilder (manufacturer) who performs such operation is liable for tax on his sale of the rebuilt armatures. See Rev. Rul. 54-329, C.B. 1954-2, 405, as modified by Rev. Rul. 56-189, C.B. 1956-1, 503.