Tia,
I've got to generally agree with what's already been said. The reddish stuff is probably some
type of cuprous oxide, and it is truly the stuff that scares me most. If it were green and bumpy, that would be a very different story, because that
type of mineralization responds great to mechanical cleaning -- it sort of crunches off (seriously, it crunches!). The
red stuff sort of gives when you push it. Try it with a straight pin in an unobtrusive location. Touch the pin to the
red stuff and gently push. It just
indents it like the
red stuff was plastic.
I have seen this stuff get removed chemically, but in your case, most of the coin isn't covered by it and the really nice
toning over the rest of the coin would probably be permanently destroyed by the chemicals that could remove the
red stuff. Not a
good thing.
The areas of
red stuff have
absolutely been cleaned before -- there's
still marks from the
red stuff being ground down. The person who did this did it pretty well. The only way to improve it is to further grind it down. But with the amount remaining? I don't think it will improve the coin as much as it will risk damaging it.
I have seen the
red stuff like this cover
bronze disease. That is fairly new to me and I don't think it is really all that common. Most times, the
red stuff doesn't cover it. I
had a simply beautiful Justin large folles that quite literally crumbled from BD under the
red stuff. It can make you sick. But I don't think your coin is that much at risk.
Sometimes, you can only go so far with what nature left you. And I think you are there with this coin. My gut tells me that you have only a one in ten chance of being happy once you start messing with this.
So, my advice is this: look at the coin tenderly, sigh a couple of times, rub it between your fingers, admire it for what it is, and put it back into the
flip.
Mark
PS The only person who I have ever seen conquer the
red stuff is Kevin Sandes -- he literally transformed some
Pan coins by grinding the
red stuff down ever more carefully, and more carefully, and more carefully, and then by very gently "polishing" the
area so that it sort of blended into the rest of the coin's natural
toning. But he has been doing it for YEARS and sometimes even he backs off. Drop him an email or PM him for another point of view.