The original end of the neck would have been 'fire polished', it would not have been anywhere near a grinder. Here is another photo, hopefully it makes the ground areas on the inside of the neck easier to see.
If you know about any damage before you buy then you can make an informed decision, I have a couple of bits of Mdina like that, one is a big textured bottle with a large crack running down from the neck. The damage was pointed out to me before I bought it so I knew exactly what I was buying.