Yeah, looks like the stem was bleached.Okay, I'm sucked into the hellhole vortex of discussing pipe stem oxidation
The oxy bath is fine for badly oxidized stems. I always hate to say this, as there are those who disagree strongly, and as I said in another thread, I'd almost prefer to talk religion (which I hate to discuss!). My preferred soak is the B&A stuff, but it's nastier to deal with and I'd rather soak 6 or so stems at a time. With oxy I can whip up a quick batch for one pipe.
The pitting you are concerned about is probably after an attempt to remove oxidation (that's what it looks like, but I'm only guessing). Remember - the oxidation is the bad stuff that has to go. The good stem material doesn't leave along with it when you soak; however, depending on the quality of the rubber stem (some are much better and denser than others) and the level of oxidation, it may look like good stem material has left (bad pitting). But it hasn't. And the pitting is never horrible after a soak - much of it is oxidation that has loosened and accumulated and now just needs to be scrubbed off. The good stem material is just hiding beneath the gunk.
After the soak, there are, again, many ways to attack what remains of the problem, but start with scrubbing off as much of the bad stuff as you can, by conventional means. If my stem looked as bad as yours, I would certainly then hit it with 600 grit sandpaper, then either begin going through the micromesh progression or start with the less fine of the two B&A polishes.
But as Curly said, "there is more than one way to skin a cat". George Dibos has said the same thing, during a pipe stem restoration discussion - to me, directly, so I know he means it, and I know all of you take his word as gospel (as do I). So...go skin your cat however you wish.
Another old gunsmith’s trick I learned years ago, is that instead of a sharp knife, get one broken piece of glass (a busted picture frame is perfect) and put it in a box and break it into slivers.I use a small, sharp pocket knife, tilted at about a 10 degree angle. I have never lost any briar using it - it tends to ride on the original finish. It doesn't sound intuitive, but it works better than anything I have ever tried.
Another old gunsmith’s trick I learned years ago, is that instead of a sharp knife, get one broken piece of glass (a busted picture frame is perfect) and put it in a box and break it into slivers.
What you have is a series of different razor sharp edges you can use to cut with. Some will be angled, some curved.
When they dull, throw it away and use another.