Last weekend I bought an awesome plastic polish at the hardware store:

A few of the organ keys looked terrible with a lot of scratches and some had burn marks, just like this one:


After a first sand paper treatment it looked like this:

This is the result of the first polish:

And that's how the key looks now after another sandpaper and polish treatment:

At another angle you can barely see the spot anymore:

It's a tough job to polish all the 36 white keys, but the result will look very fresh - almost like new.
And I completely stripped off the paint of the chassis and smoothened the surface with wood filler:

I even made the cut-out area very smooth so that it will hopefully look pretty good once it's painted black:
