Yep, that is definitely a Series 2, still not a bad tractor, and mechanically, almost identical. A couple of other indicators are the over/under shifter and throttle moved to the console, and the lower fuel tank was made out of plastic (gave it more capacity) on Series 3, they also had a foot throttle.  Creature comfort was the main object with Series 3, and those cabs are much quieter and cleaner to work in, and the engine is easier to pull since the fuel tank doesn't tuck into the dash.

One mechanical difference, the Series 3 2-155 had a heavier over/under called the super or extra heavy duty over/under. (I can't remember which was which, as they made a heavier yet unit that was used in White 160, 185, 4-225 and some later models as well. I think that was the extra heavy duty. The counter shaft and case in those units are much bigger than any of the others.)

I would definitely pay more for a Series 3, but either one is going to get the job done.