The worst playfield wear I've ever had to deal with by far was on this Bally Spyhunter game. The game had obviously been "wet" at some point, although I don't think it was flooded. The top layer of the plywood had delaminated the entire length of the playfield, and although the artwork itself wasn't toast, the playfield was unusable. It wasn't even a candidate for touch up or a rescreen because of the extensive damage. (yeah, like they'd ever do a repro of this one!) Try to find a good used Spyhunter playfield. Eventually one did show up, and the end result turned out to be a pretty nice game. Definitely better than I had expected. New owner seems to be very happy with it as well.
Here's some video of the after:
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