The Tin Man chips are shown on the MOGH/ChipGuide MGM page under "odds & ends". About 4 shown there. There's more than a dozen different colors shown in TCR. Some with "Bally's $1" house mold; others with MGM house mold or H&C mold.

I agree it's unusual to have so many versions as prototypes, including some using some of Paulson's publicly-available color combinations of that time period (as you correctly observed).

One story that I heard (but may or may not have validity) is that the monorail, with stops at MGM and at Bally's, had something to do with a MGM/Bally's combo chip?? Perhaps as a gift shop chip ultimately, but the project was scrapped.

I thought there was a similar prototype chip with a pic of the monorail on the inlay. Can't seem to find it listed anywhere though. A mystery??

Anyway, I like these "Tin Man" chips. I have 2 different colors. They are a link to the early MGM Theme Park period when it was more highly themed with the "Emerald City" exhibit and other such designs.