Depends if the crystal is signed. The signature is usually on the inside of the crystal so won’t be damaged by polywatch. When I got my sub the original crystal was split so it had to be replaced, although there are a few new crystals about the are stupid money I think I was asked $500 for one. I worked out that the nearest GS crystal is a pa484 that can be found for $10 and needs only a little bit of sanding to fit nicely.