The cost of providing duplicates of the United States Standards for rosin, and of maintaining such duplicates in accurate and proper condition for use in grading rosin, and of keeping necessary records thereof, shall be borne by the interested persons to whom the duplicates have been issued under § 160.74 (a) or (b) or § 160.75, and shall be defrayed by an annual charge of $20.00 for each set of duplicates, payable at the end of each Government fiscal year, or on surrender of the duplicates, computed pro-rata for the number of quarters of the fiscal year during which the duplicates were held: Provided, That when any set of standards issued on loan shall need servicing more often than once in any fiscal year, in order to maintain them in accurate condition for grading, and the need for such extra servicing is deemed by the Administrator to be the result of improper handling and use of the standards by the interested person or his agent, such person shall pay an additional amount of $30.00 for each such additional servicing, plus the cost of any parts or components of the standards replaced in such servicing, and any postage charges incurred by the Department in connection therewith.