Here is a link to a January 2, 1959 N. Y. Times article about the fall of the Batista regime that mentions that there was a casino in Havana's Plaza Hotel.

http://www.latinamericanstudies.org/cuban-rebels/batista-flees.htm

Along with the known Plaza Casino chips, you can see them all on the Caribbean ChipGuide, just click below, I think we have pretty good proof that these chips are from Cuba. Note that card rooms do not have roulette, so that would rule out Montana as a likely location. If these chips are not from Cuba, then where are the chips from Cuba's Plaza Hotel? I know that the information is not perfect, but I think it is pretty convincing.