Ave!
the pit seems to be an attempt to hole the coin I think...
It is too regular to be corrosion.
That was my thought, as well; someone tried to punch a hole in a really pretty coin to wear as a necklace or perhaps to nail onto their doorway for
good luck...or maybe as just a 'test punch' to see if the coin was really silver. The latter is most likely, but who can say...?
How much more patience do you have Kevin? On coins like that, I've put a small drop of lemon juice on a blackened area, let it sit until evaporation becomes apparent (5-20 minutes), rinse thoroughly, and then rub with the flat end of a wooden toothpick. Takes forever but the results are quite pleasing and little chance of damage to the silvering.
C'mon Jon, by now you should know that I have NO patience (we'll, not much) when it
comes to cleaning coins.
That's my gig, afterall: it's what I do, ya know?
Okay, I'll progress further and present further pix.
Best,
Kevin