1865 Peru Un Sol With Unusual Alteration

I must say that I have never seen anything like this before.

I can already tell you that this is not one of those counterstamped coins for use abroad. That counterstamp was placed in the middle of the coin on top of the coin, not through the coin and certainly not with a dark-colored gemstone-like addition to it.

My first guess is that this poor coin might have been punished by an amateur to turn it into some jewellery or so (maybe to hang it on a necklace). Which is a shame, because otherwise it'd have been a very nice coin (perhaps someone misunderstood the term 'gem coin'? ;) ). If I find out more, I'll post it.