My understanding is that the inlays are "coined" stainless steel, struck with a die in a coining press. The circles are from polishing the die and are probably intentional. After some use, the flow of metal wears down the rings on the die and the rings becomes fainter. After enough use, they disappear completely. You will find chips in all stages of die wear if you look at a lot of them. I no longer consider them a true variety, but still collect one of each if I can find them because lots of other collectors believe they are different.

It's hard to imagine that a manufacturer would cut wafers off bar stock to provide the coin blanks. Would be pretty expensive. However, I have no direct info from the maker of these chips.