Bought this on a lark! Obviously a labeling error, but I thought it was cool. 5th tier slab. Really a 39-D, really AU58FB, maybe cleaned. I'll put it with my Moonlight Mint Mercs.
Not only not an O mm, it's not FSB as well.
What @jesbroken said.
Looks like a label intended for another coin got swapped in the slabbing room.... Cheers, RickO