I don't have 1st hand knowledge of the events but "Banned" is the wrong word from what I've been told.

In the "old" days most of the suppliers made funny dice for anyone that wanted them including the illegal and legal casinos. Christy Jones Company broke up in 1965 not long after a raid by postal inspectors looking for records of funny dice sent to a drug store in Biloxi. Mason advertised all sorts of cheater equipment, in a catalogue put out by their subsidery The Kansas City Card Company. I have one somewhere around here. I understand they had 2 phones in the office. One was answered "Mason" the other "KCCC."

Many of the illegal KY clubs bought funny dice, rigged roulette tables, etc from BC Wills, Hunt, Jack Todd, etc. The roulette table in my Arrowhead Inn articles came from BC Wills.

I have 1st hand information that one of the largest suppliers in LV, records were purged quite often (in those days) to make sure no records of funny stuff could ever be found.

Back to your question.
I've been told, there was an investigation (pertaining to dice) and TR King made a business decision to not sell in NV to avoid the investigation.

I know you have seen the Fremont $25 counterfiet for sale. I think it was made in conjunction with a counterfieting ring operating out of Kansas City in the 1950's-60's. I believe the blanks came out of the Mason Office.