Do you have any better pics of it?
What do you plan on using it for???
Are you sure it's a M105A3?
Im guessing since there's another one next to it that this is a government liquidation. Just so you know they are ridiculously heavy... like 2500 to 3000 lbs. They also have breaks that go bad so if they brakes are bad your going to have a hard time moving it. Only reason i'm saying it is because I've actually seen and used one. We used a 3/4 ton to pull it and you could definitely feel it even when it was empty. I've always wanted one but they are not practical for an Xterra... You need a big powerful truck to pull that thing. There's a reason why you only see them behind military trucks and humv's. That trailer is too much for an Xterra regardless of generation.
Also keep in mind that tires for that ***** are expensive!!! Parts will be difficult to come by and expensive...
However if you can get it for less than $200 and want to try and restore it a little... I'm sure you could flip it and make a couple hundred bucks.