I get a lot of watches that have had really botched crystal polish jobs. This is mostly due to power buffing out deep scratches in localized areas which result in a wavy surface. If your crystal has deep scratches that cannot be removed by hand buffing, they need to be hand sanded out with 600 grit wet sandpaper. This needs to be uniform sanding over the entire crystal. I then use a 3" buffing wheel and C-Clear (by Grobet) for the initial buffing. The buffer is variable speed an SLOW wheel speeds are a must! If you run it too fast, you can melt a spot on the crystal and that usually cannot be corrected. This is followed by Polywatch hand buffing. This will result in a crystal that really does look like new. Besides the Monaco, there were a lot of vintage watches that had plastic crystals that are no longer available anywhere.
That said, I would practice on something besides a Monaco crystal for starters. Craig

: Yes, I'm also a fan of Polywatch. Grat stuff, just be careful not
: to take too much of the acrylic off!