The NW-SE lines on the reverse are disturbing. Certainly point toward being cleaned. Appears to be FSB. If cleaned I'd go with net AU-55. Otherwise low MS- (dull surfaces)
I do not believe that is the case for FB Mercs. To wit, look at the bottom band, and tell me if you think it is split/full.
Nice. I was going to say MS60 but it lacked some luster. I would of been close. Nice coin nonetheless.
p.s. Personally, and setting aside the luster (or lack thereof), if I were buying these coins this is EXACTLY the type of strike I would be looking for. It is absoultely hammered everywhere except for the bottom band, and can be bought for a fraction of the FB-designated coins. To pay multiples of price because of a strike characteristic on less than 1% of the coin seems silly, to me.