I have backglasses for '60 Williams Nags and '75 Gottlieb Quick Draw. Both are in what I would call 'OK' shape - 90% of the paint is there, typical red paint loss in the QD, paint missing on the jockey cap on Nags. I'm certain some people have these games with backglasses that are in much worse shape.
I purchased repros from Shay so don't need the old ones (even have the boxes from Shay that I'm using to store them).
You can PM me for any more information. Free for pickup - I live in St Louis, Mo.