I'm not sure why that should be. I was looking on Gunsamerica and the few SS 239s were more, but the SS 229s were not.
So I would say, shop around.
As to your original question, you MIGHT be able to get whatever it is off, but not easily. It isn't paint. You are too likely to end up with a SS slide with black still in the lettering, rounded edges and discoloration in the process.