Interesting distinction and I'll have to remember that. (Ha Ha, I'm 76 now) for the future.

But it makes sense, promotional chips are one side possible "real use" design and the other promotional. Sample chips are both sides as might have been for an actual order or sample, or prototype.

I'm sure I have some from many years ago, that are a real casino design on one side and Chipco marketing on the other. They aren't samples... they are promotional.

To be honest I never really made much of a distinction for any case, as I considered them all sample chips, used for promotion, once they were notched. It's pretty difficult to say a notched chip, is actually a prototype vs promotional, unless one has the final design as well. It's getting complicated.