There actually are *real* Pin-bot backglasses, but they were used on the "Unidesa/Cirsa/Stargame" versions of this game. But yeah the US Pin-bots which are the majority out there are translites.. many people have sworn theirs is not a translite until they look very close. There was actually an RGP discussion on this last year and someone had said they really did have a backglass & turned out to be that they owned this Unidesa Pin-bot. Pretty neat.. check out the playfield differences too (IPDB link below).. looks a bit different
See here: http://www.ipdb.org/machine.cgi?gid=4130
"Notes: This is a customized version of Williams' 1986 'PIN·BOT'. Williams supplied some of the Pin-Bot parts in a "kit" form to Unidesa. The documentation in our Files section describes the kits as consisting of "various playfield and electronic parts" and indicates that Unidesa would make their own backglasses. A quantity of 750 kits were ordered by Unidesa, but we do not know if all of them were made into full games."