K1000 repair question

I'm in the process of trying to repair a k1000 i have. Actually i'm trying to clean it. There seems to be some mold in the mirror on the inside so i'm in the process of removing the top cover. However, I can't seem to get the speed knob calibration plate off (of the ISO plate). I'm following the k1000 repair manual to the T, but I'm thinking I need a special tool to remove the plate? Does anyone know? :