I have a Solar City that looks like that inside, and it has more than 70,000 plays on the meter...many Gottliebs I've seen have excellent plating that somehow stays shiny and barely corrodes. It probably helps if it wasn't near an ocean or a smoky bar or an industrial city.
Our Jungle Queen is definitely an unrestored original, and it has very shiny plating. Maybe Gottlieb used some sort of clearcoat at the factory.
I always love the quality of the Gottlieb wiring harnesses. Those also survive sometimes in almost perfect condition. Some of those machines will probably last 200 years or more if we take good care of them and hand them down to the right people ...
Sometimes, I suspect we are running into older undocumented restorations that have passed from owner to owner. Maybe somebody stripped the playfield down and tumbled all the parts 10 or 20 years ago, and it's just starting to show tiny bits of corrosion now.