The die is engraved then the MM is hand punched into the die. What you see is the movement of material caused by the impression of the MM.
Appears to be a strike from the tool that caused the MM to look like it took a hit. If that's the case, I wonder how many others are out there that look the same? Love those Buffalo's.
I can never wrap my head around the fuss and collectability of the three legged buffalo. Many many comments on CT of the worthlessness of coins produced from over polished dies and grease strikes. Why is this buffalo over polished die any exception?
It woulda been a hoot if you were around when BNB Analytics bought his 3 legged Buffalo. I kid you not, that was probably the most entertaining time period in coin forum history.