Some clues on the unknown machine: The three identified machines are Williams machines, so it might be that the unknown machine is also a Williams, because some operators only dealt with one manufacturer. Big clue is the color of the pedestal the backbox sits on is a red/orange color. I think most Williams machine of that era had a black pedestal. It could be a 1-player machine, but the angle of the photo might hide that it's actually a 2/4 player machine. Also, the three identified machines were released in 1971-1972. I'm assuming the unknown machine was released in the same time frame - 1971, 1972, early 1973? Trying to match the backglass art shapes and colors, it looks similar to a Super Star , but that machine had a black pedestal. It's still a mystery ?????