Originally Posted By: EdwardC
I'd suggest replacing it as well. It's definitely doable, but I wouldn't say it was worth it. Assuming it's a flat round crystal, you can get order one of those for a few bucks, and a crystal press for about $15 (or take it to a watchmaker). If it's worth it to you, you can take this opportunity to upgrade to a sapphire crystal, which would be probably be in the $20 range for the crystal itself.
However, if you do want to polish it (or maybe it's an oddball hard to find shape), you'll need some diamond paste, and likely a few different grits to move material faster. I've purchased a few vintage watches that had obviously polished crystals, you can easily tell in the reflection since the surface isn't perfectly flat anymore. It didn't bother me too much, but was very noticeable. I swapped out the crystal ultimately when I sent it out for service ultimately.
If it is flat no way, domed maybe but why even bother.
I think the practice dates from when a lot of crystals were domed acrylic and you could actually polish them.