7 C.F.R. § 46.20
An identifying lot number shall be assigned to each shipment of produce to be sold on consignment or joint account or for the account of another person or firm. A lot number should be assigned to any purchased shipment in dispute between the parties to assist in proving damages. A lot number shall be assigned to each purchased shipment of similar produce on hand at that time or received later while the consigned or joint account or disputed lot is being sold. A lot number shall be assigned to each purchased shipment which is reconditioned if the seller is to be charged with the shrinkage or loss. The lot number shall be entered on the receiving record in connection with each shipment and entered on all sales tickets identifying and segregating the sales from the various shipments on hand. The lot number shall be entered on the sales tickets by the salesmen at the time of sale or by the produce dispatcher, and not by bookkeepers or others after the sales have been made. No lot number shall be repeated within a period of 30 days after the last sale from the preceding lot to which such number was assigned.
7 C.F.R. §46.20