factory windows

[Innuendo]

HR bpnnet spear and over riders are possible Nasco Options..

Yeah that is true enough, but the likelihood of these being ordered at new for a commercial model is next to zero.
Of course if a purchase receipt can be produced to prove it, I'd eat my words. Though I don't expect to be snacking on them any time soon!

It's a cool old bus nevertheless.

Supposedly prior to this system "No Dot" equaled "0" I.E: 1960, 1970, 1980 etc

Hmm, my 1960 FB has a dot on the 10th letter of Armourplate (above the "t") so I'm not convinced on that piece of information.
The good news is just about all pieces of glass are marked the same in that car, the two that don't match (you guessed it) no dot!