How old is the plate, are there plate stickers that show the last time the registration was renewed? I see there is a plate on that trailer, beat up pretty good too, but it belonged or belongs to someone... It's usually 30 - 60 days for the abandonment rules to take, but by then it would be towed. How could you "make sure" that it did not belong to someone? You would have to call the police, run a tag check, they get a hold of the registrant, he says they (you) can have it or they say it's not in the system, we can't get the guy, it's yours; or no, they get the person and they say I have to come get it. At that point the cops tell you, it's all yours (if he said, let it go), or this dude has XX days to come get this before WE take it, and you can pay the impound and tow fees to get it. Just playing devils advocate, you can be perfectly fine for all we know, it's cool though, with some work it should look decent.
Here is a story: We saw an abandoned Dodge Tradesman on the side of the road for FOUR WEEKS. We owned one, and we needed parts, getting to where I am going? Well, guess what? The cops stopped behind my cousin on the OTHER side of the highway, with the flashers on (I told him NOT to use them!). Well, we were INSIDE the abandoned van, with sockets, ratchets, and screw drivers; we panicked when the cop flashed his light over towards the van, and jumped out of the van, and ran down the hill side. Cop saw us jumping out, and then made my cousin get out of the our van. The cop asked my cousin a bunch of questions, my cousin played dumb, so the cop said he was arresting him, and putting an APB out on us, as two white males, bla bla bla. So, the cop asked him one more time, WHAT are you doing? My cousin told him what we were doing, why, and all that... You know the cop said? "Next time? Don't put your flashers on, I would have driven right past you. I don't want to see you here again, git! Go pick up your buddies and go home." Cop left, cousin came and picked us up on the lower road.. We were hiding in the bush, in the RAIN, we saw him approaching in the van, so we got in, and had our story to tell... I told my cousin though, SEE I told you not to use the flashers...
Even though that thing was clearly abandoned, it was still theft... That thing sat there with yellow stickers in the window, which notifies tow companies they can tow the vehicle. Well, even THEY know, if it sat there THAT long, no one is coming for it, they loose money. The next day? The van was gone...