John, You say:
"why would a casino in Las Vegas, who already has chip suppliers, go to a reasonably unknown chip manufacturer in NY and purchase only a $ .25 chip?"

They did not go to New York!!!!!

Only 3 companies in the world ever made clay compression molded chips.
After 1946, only 2.
95% of the chips's made after 1946 were made at Burt in Maine.

The chips were sold by distributors. If, say, B.C. Wills or Christy Jones could get a good deal on X mold overruns they would take it and pick a few extra bucks. Remember hot stamps were put on by distributors, not BURT. If they ordered a certain mold and the orderer back out, they would sell them whereever they could.

I have seen proof that Langworthy sold 4 different molds to the Dunes. Question: Why wasn't they all HHR.