Could be put on from someone else's restore. The three TZ's I've ever worked on, none had those..

your game was likely made, when they were having a bad day

manufacturing places use stickers for sorting good/bad quality stock

if furter inspections are required, initials, or date can be added

Hmm, One of the 3 Secret Service pins that I fixed up, had bright green neon circle stickers all over the underside of most of the plastics. I never figured out why. It's the only time that I have ever seen them.

The only time we use round colored stickers like that is on our annual inventory here at work, to indicate which items have been counted. Doesn't explain why you would find them on an end product such as a pin, but it could be something as innocent as that, perhaps a quality control check or count system used in the assembly process, something like that.

Scratch that, reverse it.

i found one of thos on the bottom of my whirlwind playfield last night!!

Could have been they did inventory before/while your game was being built and these got counted as a sub assembly