I asked this very question to Jim Blanchard, previous owner of ASM/Burt Co., more than a few years back and this is his reply:

"The mold was made in 1953 as I recall and never left the factory until the mid 1980's. Any chips made by TR King in the 70's were made on a different mold. Pauson received the mold from and I'm sure they made chips on it in the 1980's."

By "factory", he is referring to Burt & Co. Steve Wynn did own the GN. I believe there is also a TRK reference in the Jame's Chip Guide that has a similar reference. Not sure where that info came from.

Best,
Greg