Pics would always help, but- no 'P.38' on the side? I believe then for 480 and no-date, the serial number was on the left side, along the bottom edge (ie not visible until removed somewhat). SNs were on the toe for ac41s, along the side on the bottom for ac42 until they quit marking SNs. Proofs should always be 359.
Better knowledge will correct me- I am no expert!