I heard from Tom Sims and here's what he had to say about them:

The Dream Cafe chips were (perhaps still are) used in a home game in Minneapolis that was run by Steven Brust. A friend of mine played in the game and gave me a chip. I believe it was a $10/$20 game and probably holdem.

Steven Brust is a noted science fiction author who moved to Las Vegas a few years ago from Minneapolis. I met him over lunch once or twice with my friend here in LV. I'm not sure if Steven is still in LV or not.

Tom is also adding chip scans to his web page:
http://members.cox.net/tomesims/List.htm

Thank you Tom Sims!