Pete,

I'm not sure they were ever used in a casino. I tried to find out more information on these 18-20 months ago. The chips are marked with the insignia and logo of the Eastern Shawnee Tribe. The Tribe is based in Senca, MO or West Senca, OK. (See http://www.eighttribes.org/eastern-shawnee/ ) They operate Border Town Bingo. I talked to a couple of longtime employees as well as a manager. All said they never had a casino named Golden Broken Arrow.
One person did have an idea where they might have come from. Many Oklahoma Indian casinos work with outside companies who provide everything for the games for a cut. Some have built entire casinos for the tribes. I was told that one person the tribe was involved with (in a black jack coop) that might have been a bit on the shady side.
It is possible that he used his involvement with the tribe to cover an illegal gaming operation somewhere else. It has happened before in another instance I am aware of. The chips I have match as set of 25cent tokens almost perfectly on one side (tribe insignia). These tokens did come from Bordertown. The other side is marked “Native American Amusement Corporation”

Rick