It looks like a slight bit of wear on the reverse, to me. The Eagles wing tips, amongst other high points on the reverse.
I know it's probably a 64/weak strike... but I saw some darker/mushy areas -on the rev: eagle's chest as well as on the obv: hair above the ear and eyebrow what made me think it could be a 58.
I was debating whether to buy this coin, but I've decided not to because of the weak strike. It's one of the worst strikes I've seen on a 64.
Yeah, it is a very attractive coin, but the weakest 64 I have ever seen. The reverse is especially weak--the eagle looks naked. Shame, as the surface preservation is pretty nice.
While I do agree it is a weak strike...1890-O is well known to be among the worst struck Morgan years (1892-O is considered the worst). So, this strike isn't too surprising and the surface preservation is quite nice.