I have a 1955 Williams Can Can which is a rare and amazing game. It is a pinball machine in a gun cabinet and there are dancing can can girls who flip over and show numbers on their rears when you hit bumpers and rollovers. But my game had a terrible backglass with a large amount of ink missing. Because it's so rare, there are are no repro back glasses available.
Michael Schiess of the Pacific Pinball Museum told me to contact Steve Azzam (firstname.lastname@example.org) who makes custom repro back glasses (for not much more cost than a traditional repro backglass). Well, he took my scans of my bad backglass plus photos of a good backglass from Randy Peck and created a perfect repro Can Can backglass for my game! I highly recommend Steve for anyone in a similar situation who needs a repro backglass for a rare game. Steve has a process where he prints on glass (including the back light mask). It looks great.
I've attached before and after pictures below.
I'm not associated with Steve, except as a customer. Get in touch with him if you need a repro backglass for you game.