Great find, it for sure needs to be saved. Looking at the fact that the starter is missing and it looks like it has been sitting a while, so you dont know engine condition. MM diesel engine parts can be spendy along with fuel injection pumps.
It is rare, but MM rare is different that JD rare. Having had both, a rare MM will usually cost about what a common Deere numbered tractor might cost, unless its an R Cab or UDLX, or something with MFWD. I would say thats a $1500-2000 tractor, so about scrap price. Complete and running order, $4-5000.
Keep us up to date on what happens with it.