Applies to the mfg. of porcelain ware pottery by a mechanical press forming process. Contemplates porcelain insulators, spark plugs, ceramic cores, ceramic wire spools, ceramic tiles that are decorative rather than structural in nature. Codes 4061 and 4062 shall not be assigned to the same risk unless the operations described by these classifications are conducted as a separate and distinct business. Mining, quarrying or clay digging to be separately rated. Refer to code 4036 for the mfg. of cultured marble products.