It looks like a Four Seasons to me. They seem to have closed up shop in the early 90s and don't have any web presence but they were built in Colorado (they had an address in Denver and in Ft Lupton--maybe office and factory?) and have that lift system and very low-profile cab-over. They also built some Toyota motorhomes
http://www.flickr.com/photos/toyrv/sets/72157622089052576/. I have an '88 Four Seasons Magnum (longbed compact truck) and that one looks like a larger version of mine but with a wrap-around rear end. One giveaway would be if it has the back door that goes all the way to the top of the camper body without a solid strip between it and the roof and a velcro soft-side panel to close the space above the rear door--I imagine they all used that design.
That bed trailer appears to be a long bed. The camper looks like it would be a perfect fit if it were slid forward a little. I bet it's a 9 1/2' camper for a full-size long bed.
These campers may have a similar truck-fit issue as the older four-wheel campers, in that many of the older campers don't fit in the newer trucks due to tailgate-bed width. A lot of newer trucks tend to run a little narrower in the tailgate than their predecessors. Try to get a camper width measurement from the owner.
The HMD TL the seller is referring to is the title designation of the truck bed trailer it's sitting on, not the camper. It's the designation for "homemade trailer." I used to have one.
My camper is holding together pretty well. The main weakness is that rear door setup. Because there's no solid framework above the door, the sides of the camper have a tendency to widen at the back. Mine got to the point that the back door wouldn't stay latched. That also affects the way the roof closes over the top campers edges. I just added a piece of tensioned steel strip across the top of the door opening (and covered the exposed part with pipe foam insulation so it doesn't inflict pain) and it's worked really well. Now the door has a tight fit. The windows in the soft sides are in pretty bad shape on mine. The clear plastic windows are discolored and cracked and don't close all the way and the screens are pretty ripped. It may just be mine though. Otherwise, I've been happy with the build quality, even off-road. One gripe is that the extra thin cab-over is a little limiting in that you can't really store much of anything under or above the mattress. Even some 1" eggshell foam or a sleeping bag are too thick to close the roof on. They have to be stored elsewhere. A lot of designs have taller cab-overs sections with extra room for bedding, etc.
When I got mine, the back door wouldn't open without lifting the camper roof a little. That got to be obnoxious so I cut off the top aluminum flashing on the door. Now it opens without having to unlatch the roof.
They do seem pretty good at sealing out moisture--no roof leaks, etc. Do look under the cab-over mattress through in the front corners and look for darkened wood/odd smells. Mine accumulates a tiny bit of moisture in the front corners of the cab-over under the mattress when it's parked but it hasn't been bad enough to cause rot. Out camping, it keeps me completely dry.
At first I would have guessed that that one is a little newer than mine, based on the siding color/stripes and cabinets, but they list it as an '88 as well. Here's mine before the repaint, with the 80s Four Seasons stripes.
I'll try to research the older phoenix then. I did see the side droop on the roof but the owner said no water damage. 
