A mobile device operable with keys 14 having characters 16 engraved onto the surface of the keys. To provide back illumination, visual traces of the characters are provided by a plurality of holes 18 made to the keys to provide spot light outlets adapted to collectively define the traces. The holes can be drilled and the key caps can be made of steel or other metals. The grooves 16 can be closed by a translucent material such as resin to block the ingress of dirt into the holes 18.