I really like the test units with the holes in the sides of the cabinets in engineering.

06---engineering-dept_-3a8404f.jpg

Model 315 is Pop-A-Card, which came out in March of 1972. The tour was around the end of 1971, based on Lawman/Sheriff being in production (it was released in October 1971), so it seems quite a few months passed between initial engineering and finished game.

If anyone wants to see all the individual pictures, in slightly better quality, they are here:
http://www.retro-flip.com/t2429-GOTTLIEB-FACTORY-TOUR-IN-71.htm

The photos are from 1971, based on the game on the line at the time (Sheriff/Lawman released in October 1971), plus all the references online saying this is a factory tour from 1971. I was saying that it's interesting that Pop-A-Card (which is pictured in that engineering photo with 315 written on it) was already far enough in design to have a backbox laid out in late-'71, but wasn't finished until March 1972. I think its neat to see how long it took that game to go from an early test state to a complete production ready unit.