There are online communities dedicated to modding and improving casio watches ... here is a modded F-91W: http://forums.watchuseek.com/f17/casio-f91w-mod-negat

There are online communities dedicated to modding and improving casio watches ... here is a modded F-91W: http://forums.watchuseek.com/f17/casio-f91w-mod-negative-display-diy-757778.html http://forums.watchuseek.com/f17/casio-f91w-mod-negative-dis...