I agree with Joe. A blob like this could be from fire damage but not when it i the only sign. The rest of the surface is in fact in
very good condition. Fire damage can't be that localized.
So other options:
- sign it is a cast?? I see no other signs jumping out at me but has to be considered and examined.
- evidence of a weird pit in the die?? If so a very odd one.
- could it be a blob of molten silver that dropped on it from another coin or object that melted near/above it?? Starting to stretch occam's razor here......
SC