It's not for a Massey Ferguson. If you look at the opening in the nose housing where the pinion gear is, your opening is not parallel with the mounting bolt holes, it's at an angle. Massey's starter(and a lot of others like it) has the opening parallel with the holes. First link has a 12 volt starter with the angled pinion gear opening. States it's for industrial/marine uses and lists Prestolite cross reference numbers. 2nd link shows some applications.

Massey Ferguson starter

References:

https://www.ebay.com/itm/Starter-for-Massey-Ferguson-Tractor-TO20-TO30-Others...

Reason:
Another opinion was accepted instead.

This is a rebuilt Prestolite starter motor. Yours is missing the I.D. tag. Without the tag it's impossible to know exactly what it fits. You can see the two small holes where the tag once was in your first photo. What I do know is it's a 6 volt unit since it has the band on the back end that covers the brushes. 12V starters don't use the band. It's most likely this is an industrial starter and not for automotive use. I've supplied a link to what I believe is the same starter as yours. It's has the same dimensions, mounting is the same, electrical stud is in the same position and the drive pinion looks the same. The one pictured is new surplus starter that was used on support equipment for aircraft, probably a starter for a generator. The second link I've provided shows what the I.D. tag would look like and how it would mount on your starter. Please note: the starter pictured in the second link is not the same as yours. I'm only including it for reference on the I.D. tag placement.

References:

https://www.ebay.com/itm/Prestolite-MZ4181T-6-Volt-Engine-Starter-Made-In-USA...

https://www.ebay.com/itm/Mbg-4109-Wisconsin-engine-starter-Prestolite/3925259...

Reason:
Another opinion was accepted instead.

It's not for a Massey Ferguson. If you look at the opening in the nose housing where the pinion gear is, your opening is not parallel with the mounting bolt holes, it's at an angle. Massey's starter(and a lot of others like it) has the opening parallel with the holes. First link has a 12 volt starter with the angled pinion gear opening. States it's for industrial/marine uses and lists Prestolite cross reference numbers. 2nd link shows some applications.

References:

https://esellsimple.com/starter-fits-prestolite-46-2449-46-456-mbg4134-mbg413...

https://www.amazon.com/Starter-MBG4134-191-0511-46-456-46-732/dp/B01MR3AYGJ