Pretty sure Massey built them themselves.

Dad had a 620 that was manual fold, I'm pretty sure the 820 is a hyd fold that was out at the same time as the 620.  

Dad's 620 was decent as far as leveling goes.   Its biggest problem was that the gangs didn't like to keep rolling all the time.    It plugged up a lot for some unknown reason, the bearings weren't the problem.

They were new in the late 70's or early 80's.