I've now removed the paint from the door - turns out it's first coat of paint was white, then deep purple before it acquired its green and pink livery.
The backflash was completely covered in a rough white corrosion. To my surprise, this rubbed off to expose a very bright and clean backflash. Unfortunately, long splits and very bad buckling mean it's not salvageable, so it's going to be replaced. The mechanics are all there and working. It does have a makeshift internal coin drop from the coin entry to the coin chute, so I'll need to find one of those.