I took a close-up of the semi-circular line on the coin to show the milk-spotting quality of the line. I just don't know what it is to be honest, I'm a causal collector. I hope it wasn't a botched dipping or cleaning
The semi-circular line from the 3 o'clock to 7 o'clock position on the obverse doesn't reflect light when I look at it with magnification, so it doesn't look raised nor gouged. It looks like some kind of milk spotting to me, but I'm no expert.