All the cars (Norwood only?) were stamped as a QA/QC 'signoff' for Paint, Trim, and Body as they completed Fisher body production.
From the CRG reports ( http://www.camaros.org/assemblyprocess.shtml#fisher
) on Fisher body assembly process....
"The seats for that car were delivered from the "Cushion Room" where they were built, and the rear carpet and seats were installed last, followed by a final inspection (at Norwood, but not Van Nuys, "P", "T", and "B" ink stamps were applied to the body for Paint, Trim, and Body inspection OK), and the body was shipped up the ramp to Chevrolet."