did you try 90% rubbing alcohol? joe's gel may work too, but i'm not sure if he's still in business. if absolutely nothing works, you are going to have to strip the shell bare, and start from scratch. is the lettering real thick and raised? if you can run your finger over it, and feel the outlines of the letters, it's a thick pad print. if you can't feel anything, or paint color dividing lines, you may be able to just re-paint it without stripping. but, that's what i would do, if all else fails. you don't want to ruin it over a bunch of letters. sometimes, if you are patient and careful, 1600 grit sandpaper will remove the letters without harming the paint. it's a finishing grit paper, used to smooth out rough spots in plastic, wood, putty, etc. i used it on a stubborn kato sd40, and it worked, and the paint was never touched.
matt arentzen
northeastrailworks.com