With an orphaned pinball machine backbox and an urge to learn to use microcontrollers I set out to build a clock that required no batteries, could set itself to the current time and could be easily undone should I ever find a matching body for the backbox.
This project was first covered at Hackaday years ago (Thank you!) and predates the rest of the Fun With Pinball exhibit.
Details
Build details, photos, issues and anecdotes are at the Atomic Pinball Clock home page.
Part of me hopes you don't find the body, because the clock is pretty cool. Nice that you made it convertible back to its original form.