I did know that the actual Plinko chips used on the show are kept in a locked container, and there are only ten of them.
There were actually at least 11 originally made in 1982. As you know, like most every other game on the show, a duplicate set of small props exists. For Plinko, there was at least one “test” Chip used by the stagehands or staff when testing the board so that the chips on air would not get damaged or visibly worn. It would actually make sense that that made a full set for that purpose, but I can’t say for certain. I do, however, know the whereabouts of a test chip marked “Stage Right Props.”
In the end, we concluded that while his chip looked real, it was possible it came from the live show.
The value and condition (and approximate size) leads me to believe the same thing for these. I have a set of them which look very similar (and off colored from the real chip).