I believe you are right.
JD 540-640 skidder.
This time they decided to play with model number too, since usa lawyers are more dangerous than russian (ural, uaz, zil (rip), kamaz), Ukrainian (kraz, luaz, zaz) and Belarusian (maz, mkzt).
(So many "z"...its "zavod", plant. A - automobile, other letters - location of zavod, or name of lenin in zil, both dead already...we didnt use fantasy when naming vehicles)))
And took away these safety frames.