Back in the 70s, I passed by a similar trailer every day in Berthoud, CO, between home and work. It sat behind a service station and never moved until it disappeared one day for good. I would guess the trailer length at about 24'.
The one I saw was custom designed for a specific mid-sized US car. I don't remember the make, but I believe it was a Ford. The underside of the trailer front end was shaped to mimic the shape of the rear of the car. I remember thinking that they didn't want to get high-centered over something like a railroad crossing because there was not much clearance between the car trunk and the trailer.
The front end of the trailer would not have had much vertical space over the bed. It would probably have been a lot like sleeping in my boat where I could barely turn over.
The hitch was a pretty sturdy-looking weldment that clamped to the rails at the edges of the car roof in four places.
John W. Irwin
2005 Classic 28 "Sabre-Dog III"
2013 Silverado 2500HD Duramax/Allison LTZ
WBCCI #9632, TAC TX-10