was always...who would authenticate the chips?

Did the slabbing companies have someone who knew the difference between an authentic chip and something that was manufactured after market? Probably not. What would the authenticator do, look in The Chip Rack to see if the chip was authentic? (And other chip guides for non-Nevada)

Oh...and as far assigning chip value...the occasional box of chips still turns up and changes the value. I remember a few years ago someone sold a Sunflower, Reno, chip on ebay. About the same time that the auction ended, there was a "find" of the same chips. I don't remember the details, but I don't think the seller was involved with, or knew about, the find. As I recall, the seller refunded a portion of the payment back to the bidder, because of the find.