The "Holy Grail" of dealer signs is the R778, which is the fullsize case with a glass front and "McIntosh ... Made in the U.S.A." as the lettering. There is no switch on the unit - you just plug it in and a flourescent light comes in a couple of seconds to illuminate the sign.
Attached is a pic of the R778 from Bernier's website.
I was lucky enough to get an R788 at a McIntosh dealer who was retiring/closing down after several decades of being a dealer. I got the sign for a phenomenal price, partly because it was clear that I wasn't just going to throw it up on eBay. Not only did I get the sign, but it came in the factory original and correct R778 double box!