Factory Original 1969 Barracuda Dart 340 383 440 Paint Inspection Markings

Don't mean to hijack this thread but it's old (like me). While removing the undercoat off the firewall of my 69 Barracuda, I found this marking under the original paint. It's not a number like the similar photo in this thread. It's hard to tell in the picture but I can see the tracing under the paint and it's an SS. Not sure what that means. Maybe the initials of the guy who inspected the body prior to paint?

Paint marking.jpg