Resurfaced Encoder Disk
I went back and soaked the encoder idsk in acetone for a while to remove all the old polish and then carefully removed contamination and re-applied a layer of clear polish. There's a sticky layer that the acetone was attacking between the plastic and the metal. If I thought it was just holding the plastic, I'd let it soak until it came off, but I suspect that the slots are printed on the plastic and then that's glued on the aluminum.