B. C. Wills & Co., Detroit MI and Reno NV, were the distributor from 1937-1965.
Chips actually made at the Burt Co, in Maine.
We call them Small Greek Key mold.
BC Wills called them "Wills Gem Checks."
In these years only 3 companies made clay compression molded chips. TR King, USPC, and Burt.
There are 1000's of Greek Key chips out there that are destined to always be UFC's.

Poker Chip Store in CA bought both the small and large greek key molds several years ago and are selling them today.
Chips now being made at Blue Chip Co in LV.