If I had to bet a lot of money ... I'd say it was done in a "factory" environment at least. I think I can see a rolled edge from a punch, and I can't imagine an off the shelf punch and die with just the right size and radius .. that would also fit in that cavity. However it also wasn't punched before the lid was stamped, no way the sheet metal would hold up to stamping with the slots already punched.
Could have been done at the same time as the stamping, but that would mean it would have to be "factory" or done by a sub-contractor at least.
Makes me wonder if it was some oddball police package part, or obscure aftermarket piece.
If it was for sale from either the Detroit area, or a place like Washington state close to Boeing etc. .... lots of people with access to lots of high end shop equipment back in the day producing things with company equipment for their own projects.
