The trailer is a Jackwagon Basecamp. I bought it used just a few months ago. So far, I'm really impressed with it. Tracks well, and has no problem on rough roads. Aluminum box measures 6' long, 4' wide and 2' deep. Payload is about 1,000 lbs. Rides on a real nice suspension and this one has electric trailer brakes.
The manufacturer is down in Arizona, and they offer a lot of custom options that don't seem to be shown on their website.
Link:
http://www.jackwagonoffroad.com/