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Looks to me like oxidized Vulcanite. Polish will polish it, but not take off the color. A bit of fine sandpaper followed by very careful (the stuff is soft!) buffing with a fine compound should...

A picture might help us give advice.
If it is UV based, and you can't get it even by hand, look for someone you trust with a buffer. If you don't have a local friend with said implement, then you...