I always thought they were Las Vegas also. Before your find I picked up the $5, $25 and $100 black with 8 cream edge inserts, one of each. James lists it with 8 Lt Blue edge inserts, but I think his photo is off color and he never had the chip, my black $100 had cream or tan inserts. They were in a box with other rare Las Vegas chips mainly the FLAMINGO 25 red with 3 yellow SmKey. I picked these up about a year before your find. I sold them about 3 months before the big group came out. Well, that is the little I know about that chip.
Glad to see you posting again. I always enjoyed your shows.
Having fun Steve