I just cleaned my clear PONG in a 50% ISO solution. I put the ISO and the PONG in a plastic freezer bag, swished it around for a few minutes, cleaned it out with cotton swabs and rinsed thoroughly with water. The PONG came out clean and showed absolutely no signs of discoloration or damage.
Usually the damage from solvents is over time, and not something you would notice right away. Not unless I am misunderstanding your post?