More interesting discoveries
The left popper assembly was broken: one of the two lugs holding it to the payfield had broken off. This is apparently a common fault with this assembly. Also, even though I thought it was by design, the metal assembly has a convex dent in the upper surface. This comes from the repeated hits from the pinball as its shot out of the popper:
Left popper assembly with broken lug and interesting bulge
The plastic lane guides had also taken a beating:
Plastic lane guide assemblies - or what's left of them