It's an M1A1:
Several design chances can be distinguished between the two, such as the lack of a CITV sight on the M1A1
Which is present on the M1A2:
M1A2 can be equipped with ERA and slat armor, this makes the configuration M1A2 TUSK:
M1A2 SEP further adds newer features including heavier DU armor, new ballistic shields for the secondary gun and the CROWS turret:
There was also a version called M1A2 SEP TUSK, which combines all of the above improvements into a single package, though this particular tank lacks the CROWS system:
M1A2 SEP V3 was recently unveiled publicly - its improvements are internal and include new ammunition, FLIR and a lower profile CROWS system: