Example. If the operator mixes three equal quantities of material in a day tank and treats that product as a three-part mixture in its production unit, Customs will accept the resulting product as composed of the three materials. If, in the alternative, the operator assumes that the three products do not mix and treats the first product as being composed of the first material put into the day tank, the second product as composed of the second material put into the day tank, and the third product as being composed of the third material put into the day tank, Customs will accept that convention also.
19 C.F.R. §146.95