I found this on the Alabama Boating site:
HULL IDENTIFICATION NUMBER FOR MANUFACTURED VESSELS
All vessels manufactured after 1972 are required by Federal Law to have a hull identification number affixed to the vessel by the manufacturer. This 12 digit number is normally located on the outside stern of the vessel on the right side, below the gunwale. This number must be included on the registration certificate and application for registration.
Boat owners with vessels manufactured prior to 1972 may apply with the Marine Police Division for a hull serial number which will be affixed to the transom of their boat.
Look very, VERY closely at the transom. If the boat was painted since it was originally built the PO may have painted over the numbers but the impression may still be there.