so you can have my full 2c worth. At the time those chips were made, the centers were 'spun'. All would have had those concentric circles. A lot of the time they get polished off in the finishing process. They also wear off with use.
Later coin inlays appear to be cast rather than spun (although not exclusively). It does seem strange that there is only one single example but I doubt its a 'prototype' or any form of sample or it would have been 'notched' by the manufacturer.