Posted the 11th day of May in 2011 by Riley.
El Xispas has posted an excellent how-to guide showing the cleaning up the crystals of some old beat up G-Shocks. The original post is in Spanish since it's over in the Hablemos de Relojes forum. There's lots of photos of the entire process. It looks like some careful polishing with the right tools can make a scratched up crystal look like new again.
|G-Shock crystal before and after|