Before it was modified and called Space Time, Bally built 70 Time Tunnel machines. Probably less than 1/2 of those may still remain.
Apparently they had copyright issues with the name and a television show, so it got scrapped in the original Time Tunnel theme.
A pretty nice looking one is currently up on eBay here.
At some point I’d love to collect the rare stuff, but that isn’t in the cards now. I’ll just have to settle for playing Al’s Varkon often. “)