It looks like dirt to me. With all due respect to the opinions of others, I don't see any historical value in dirt, even if it's stuck to a historical object. (Wow! This dirt is old! Isn't all dirt?) I remove dirt all the time from uncleaned coins... which actually increases the value of the coin. I don't see how taking some dirt out of a hole can be equated to removing the
patina of the coin.
There are a lot of times that over-cleaning makes the coin look worse, and some deposits can serve to highlight the details of a coin. Other times the deposits can serve to cover up imperfections and make the coin more aesthetically pleasing. I think that this is the case here.
On the
flip side of this coin (pun intended), you could also argue that the hole is also
part of the
history of the coin, maybe being bored into the coin to be used as
jewelry or to be hung up as a charm, souvenir or religious
amulet. By covering up this hole, you are concealing a historically important piece of this coin's heritage.
I don't mean to come across as sarcastic, but re-reading this... I guess I am. The fact of the matter is that the coin looks
good as it is. The rule of thumb that always seems to apply is, "If it ain't broke..."
Regards,
Danny