Main belt tensioner - part of ac unit?

I bought a new tensioner pulley for my serpentine belt - It almost appears the old one is part of the ac unit. Has anyone seen this? Been trying to remove - no visible bolts (on the tensioner, not the ac). Whats up with that?

Year? Engine size?

Nevermind, found the nut for the tensioner stud. Hidden under part of ac unit.