I wouldn't rule out a repro. A while ago I bought a little "Expert television servicing" sign on unmentionablebay. In response to another shopper's question, the seller had stated that it was NOS. Anyway, it only cost a few bucks. It took him about three weeks to ship it (after a reminder by me). In person, it looks like something he just stenciled on his dining room table, drips and all. Still cute, but who's to say where it really came from?
There are loads of repro signs floating around nowadays, and repro radios for that matter. Someone who picks one up at a garage sale, etc., might actually think they have something old. Not everyone trading on unmentionablebay is a genius or expert
Phil