MF should have put a sticker on the fuel tank.
Reminding the operator to check the upside down cotter pin under the belly of the tractor each time you filled the tank.
I got my TO-35 stuck one year, even though I had a cotter pin in the trans drain hole, mud was stuck up in the hole and I did not drive the tractor in tall grass for a while, so oil built up in the sump and ruined the clutch.
I bought that lesson: even though I knew about the key, but just did not check it as often as I should have.
most all old fergy's will leak some, but if you keep the trans/hyd oil level at the 1/2 way mark on the dip stick it will leak less.
always have the lift arms in the down position when checking the oil level, that insures all oil is in the sump. need to let tractor set for a few hrs to be sure all oil has drained down.
remember: that upside down cotter pin is one of your best friends, if you own an old fergy,
as I was told many farmers traded off the older fergy TO-35 when they started leaking as they are harder to repair than the later models.
I do not know, mech put new oil seals in mine when it was in for clutch repair, but it did not stop the leak, only slowed it down, you just learn to live with it.