There is probably a good chance that there's a reason it was painted... if it's worth your time to find out, then good luck with getting the paint off, a friend of mine used GoofOff with great success (he could see the KI sticker underneath was in good shape), but in the end, it'll probably save you a lot of headaches just to sand it and re stencil it. I have a Robotron that's more on less the same as your Joust, I haven't bothered stripped the black paint off because I know, that in the end... I'll just want to restencil it. Even found the stencils I want to use already (EU Robotron stencils modified for US cabinets).
Just saying, but anyways, good luck with the strip. I'm curious as to how it looks under there.