Looks like monti to me too. A LFS had a very similar looking piece, and he was very sure it was "Acropora vietnamensis" Not even sure if this is a real species, but that's what it looked like. Very cool, in any case.
Think he just had is genus wrong. Here is M. vietamensis from reefaholics page:
Still don't know if thats correct, but reefaholics is calling it that. He states that it is common, but I hadn't seen one before. Hard to tell from the pic; I guess it is encrusting or mounding.
Looks exactly like what I saw. I'm 99% sure it's NOT an Acropora species, but that's what the silly LFS store boys were calling it. The piece I saw had a very similar branching pattern to M. digitata.