Hm.. This looks like an older generation M-250r2, as the bumps on the back of the fixture near the slipfitter are smaller. But its hard to tell with this picture.
not sure...it might be an NOS unit.....for example iv'e seen my utility still ocasionally install AE's even though their contract or whatever deal they had seemed to expire,and the bumps on the back are the casting where the slipitter bolts go in...though im sure you knew.