Quoted from Stu:On older games ( 80's, like Viking ) I have seen many times where the machine was not stored properly and thus the Left & Right sides of the backbox have started to bend downwards towards the floor, making the bottom channel sort of banana shaped & not allowing the backglass to sit correctly in the channel, thus not being able to lock it in place.....
...Never heard of a Repro glass for Viking....Who produced it & when?
A similar situation (I'm currently dealing with on a Black Knight) is that the top panel of the backbox can warp so that it is drooped down in the middle. This prevents the backglass from being slid up high enough in the top channel to clear the lip on the bottom.