Judging from the pictures, I believe it is a Mark 4 MR/T. It looks to be too short for an LR/T. Besides, the correct scope for a Mk 12 is supposed to be a Mark 4 3-9x36 MR/T with M3 turrets.
I'm fairly certain that the Navy MK12 used a Nightforce 2.5-10×24 NXS and the Army and Marines used the Leupold. I'm not 100% on this but I know it was a NightForce.