To the best of my ability, I believe your tiller is definitely a 1960 model 2046-01 Super Mustang.
I came to this conclusion by comparing manuals for the various years of Super Mustang tillers.
A copy of the Owner's Manual & Parts List is posted at: http://gardentractor...ng-tiller-1960/
The tiller's gearbox is filled up to the level of the fill plug with SAE 90 gear oil. ....You want it so that if you add any more, it will run out.
The engine oil should also be filled so that if any more oil is added it will run out. ....This is the correct level to maintain! ....These small engines only hold 16-20 ounces of oil, so if it is down by 4 ozs, that's a 20-25% reduction, which is not good!
I notice in your pictures that the belt guides are not in their proper positions to keep the belts in place. ....The guides should be adjusted inward toward the belts so they are approx 1/8" away from the belt while there is tension on the belt. ....When the tension is removed, the slack is directed upward toward the engine pulley, to keep the belt from dragging. ....The guides also prevent the belts from coming off any pulley when the belt is slack.