What is this disc? There is no evidence of writing or description on the underneath side. Par Plastics puts their stamp on other brands as far as I know. I'm intrigued by the two circles on the bottom, equidistant from the center mark. maybe where the arm picks up the disc after being molded? It's a domey fairway, (I'm guessing 7 speed), appears stable (like 7/#/0/2.)