When stripping and blasting a '69 charger r/t that I am working on, I've come across a factory paint marking that I'm unfamiliar with. I've stripped a bunch of these cars and to my recollection this is the first time I've seen this mark. Any idea what it was meant to indicate? The mark is either an 'A1' or an 'AI' and is on the right (passenger) side inner fender firewall area. Thanks.