It’s how Bally labeled the CPU board generations on their early solid state games.

Aside: I think the best restoration project is the one you’ll have the most passion for. Pick a game you’ll really want to put work into.

First time restorations are time consuming, and will be filled with a lot of trial and error. If you’re picking a game “just to do” you might find yourself burnt out and lacking enthusiasm.

If you pick a game that has meaning, or one you’re enthusiastic to do, the whole process is much more enjoyable.