Old Ted Award Winner
I was thinking of the same thing. Cleaning the outside is way easier than the inside. I would lean towards getting a replacement stem made to smoke with and set the original aside.You are talking about the outside of the ebonite.
Aaron is talking about the inside.
I have restored a few (several?) hundred pipes.
There is a point of oxidation ("green through and through") when it ain't coming back to "clean tasting." Particularly if you are sensitive to the flavor of ebonite, as Aaron is.
Lipstick on swine.