No person purchasing milk or cream and paying for the same on the basis of the percentage of butterfat contained therein shall, if the percentage of butterfat is ascertained by the “Babcock test,” use any test glassware except standard Babcock test glassware and weights which have been previously inspected and approved by the Department of Agriculture. If the proportion of butterfat is determined by any method other than the “Babcock test” no utensil or instrument shall be used in the determination until the same has been inspected and approved by the Department of Agriculture.