That's the same one that Doug aka DH1 posted a couple posts up, it does look a lot easier to maintain and keep tensions in check. I am putting my money on that it is the earlier model. I would love to find documentation or manuals that show that design.
I found my 620 Manual in the barn and have scanned it to a file I have called "MF
620 Snow Thrower Front Model". I will upload it after I post this reply. I'm guessing that I got the manual at the same time I got the thrower (from Rammelt & Sons, MF
dealer in Westfield, NY). It was on the front of a MF12 Hydro that I bought mainly for the tiller that was on the back. They insisted I take the thrower as well because they wanted it out of there! The manual that they gave me was apparently for an even earlier thrower, because someone had written on page one that the serial number was "145 800 1556", in other words (numbers?) 1458 001 1556. Mine, shown on the earlier post, is 1458 003 073. Mine looks exactly like, in all respects, the thrower in the manual. From what I can gather from this thread about mounting the later model, the earlier one is much easier. There is no need to jack up the tractor to slide the puller affair in place, no implement drive hanging down under the tractor to connect up, and no need to adjust the support arms to tension the drive belt (although the my 620 manual does suggest this method as the first approach). In the 30 inches of snow that we had in the Washington, DC
area last week I found that I had to make three passes, successively lowering the thrower each time, to clear the driveway. On the first pass, with the thrower raised as high as it would go, the snow remained higher than the bottom of the transmission case and would built up to the point that the wheels would just spin, so I had to keep going forward and back to the point that the snow was lower than the undersides of the tractor. This makes me wonder how well having the drive pulleys under the tractor on the later model 620 works in deep snow. This thread inspired me to go out today and buy some hollow and solid tubular rod that I can bend and weld into a chute control crank, something I did not get with the thrower.