"My guess would be that the variation is due to a Chipco ink/dye problem back at that time."

It was a "resin" problem, from a Chipco supplier.
Chipco spent over 1/2 million replacing the chips.
All chips were replaced except Arizona Charlie's.
AC's would not let Chipco replace them. Have no idea why.
John Kendall told me he was embarrased everytime someone mentioned the AC's chips to him.