I do see in his picture, as compared to the 5.5"/6" I have, that the front sits in much deeper than mine. Pretty sure now after emailing him that he is measuring properly. He thinks it might be NAPCO. I feel like, since clips don't all fall off, that it is an implement or trailer wheel from around the late "clip era".
Just a guess. Maybe someone will chime in that has 15"x 8" non-nub on something.


Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn