I can't say for sure, I haven't used the product. The old black machines were japanned and the decals were applied and the whole thing then got a coat of shellac to protect it. As long as the wax doesn't damage the shellac and the shellac is in good shape, you're probably fine. More modern machines use a painted finish and aren't as delicate. You should be good on those. Try some where it won't show and see how it does.
Rodney