Recently, I've got an HP-71B whose metal cover surrounding the display shows a brownish discoloration. The former owner of the machine says that this is probably due operation of the unit in a metallic protective case. I tried to get rid of this grime using both a household detergent and 94% isopropyl alcohol. Unfortunately, the results were poor and unsatisfactory! Does anyone know how to get rid of this brownish grime? Any advice would be appreciated! Thanks for your time!
Regards, Juergen