I was told that Simichrome will polish bakelite by a bakelite collector. He uses it to authenticate old bakelite pieces by putting the Simichrome on a cloth, then rubbing the cloth on the bakelite. If the object is real bakelite (as opposed to plastic, I guess) the cloth will turn yellow. He said that he noticed that on some of the bakelite that was faded/dull, that the Simichrome brought back the shine. He also said that the bakelite was not harmed or scratched. I have never used Simichrome on my bakelite grips, but have thought about trying it out. I have a pair of grips that had been spray painted. I used fingernail polish remover to remove the paint. It worked very well with no damage to the bakelite but, the paint had left the surface of the grips very dull and faded looking. I put Rem wax on the grips and it helped put a little shine back. I may consider using the Simichrome at some point just to see how it works.
Not sure if the Simichrome will remove stains but it could if they are not deeply embedded. It may also depend on what was added to the bakelite in the process of making it. I have notice that on some of the later grips, they seem to be more porous (maybe it is from having sawdust added) and they absorb more rust when exposed to it over a period of time. Just my thoughts though.
I took another look at those grips. The dark area could be from water/moisture damage ,like sitting in water. Maybe one of the bayonet gurus can add more on the subject.