There was a keyboard swtich sodler over here that had
a flat keytop made
in 2 parts. The top part was transparent plastic, the bottom part white
plastic. The idea was you could either label the lower part with rub-down
letters ('Lettraset') or put a paper label between the parts.
**very** common keyboard in Brazil. Way better than "THAT" of TK82C and
TK83 :)