There are a couple versions of the 451. The first was merely a re-hash of the earlier model 450. They were sold new BEFORE New Holland was "SPERRY New Holland" . (60's/early 70's) I've got one of the earlier renditions. New Holland still supports the 451, but SOME parts on the earlier serial numbered models are not available. (BTDT, retro-fitted a few parts on mine) Any decent working 451 will sell for a minimum of $400 here. One in good shape, even the earlier versions, will bring much more. Mine is 38 years old, has cut literally thousands of acres, and I've recently passed on an offer of $900.