Casio W-800h Mod ((link)) -

You now have a fully analog-digital hybrid. It is scratch-proof (sapphire), waterproof (screw-down case), and tracks three time zones. No one will believe it started as a $17 Walmart special.

Locating a specific solder jumper (often labeled on modding guides as the one to remove) and desoldering it using a soldering iron or carefully scraping it away. casio w-800h mod