Josh, the numbers are usually on the tongue near the hitch, sometimes on the bottom. I would go the DMV route first. I built a trailer a few years back and went to the State Police to have it registered and numbered. They first though I was guilty of stealing it and tried to prove that for over an hour. They finely gave me the numbers after making me feel real guilty. Now this was a home made trailer and it looked homemade. I'd hate to try and pass off a factory trailer off as homemade. Those troopers at Troop C are tough. The other way to get it done is find someone with a title for a junked trailer. You'd be surprised how many people hold on to those things long after the trailer is shot. You might even ask at you friendly notary's office. When I needed one a few years back for a trailer that I owned and mentioned it to the notary, he gave me the name of someone who had a bunch of such titles for sale for 25 bucks. In fact I would start with a good notary and tell them you have an abandoned trailer with no papers and they should steer you in the right direction.
"gene"
"G" Gone but not forgotten!!