Those look like cctv monitors.
I do cctv work and I would just say be cautious when buying them used because they run 24 hours a day with primarily the same image on the screen so screen burn is very much possible.
Going off this and another post on the previous page, I'll share my experiences.
I've had these
Mitsubishi XC3717C- beat up, flickered and popped occasionally, dark image at times. Paid $150 off craigslist. Looked like it had taken a hard bump at some point in it's life. Screen was scratch and burn-in free. When it worked right it was flawless.
Mitsubishi Diamondscan 20m- Got free from a pc repair shop just for asking. Was near mint. Perfect condition, perfect monitor. I kick myself so hard for ever selling it.
Sony PVM-1251Q- Found for free in an old barn from a junk seller. Had to search through about 20 other monitors to find this one. Was covered in mud, and manure. Once cleaned up it performed perfectly. Maybe the nicest arcade image I've ever seen since it has it's own smoked glass covering.
20" Sony PVM from auction- $20 at auction. Very poor condition, the case was halfway cracked open and the screen had severe gaussing issues. After deeming it a lost cost and fire hazard I threw it away.
20" Sony from a different auction- $20 again. This one exhibited partial horizontal collapse. I monkied about in the service menu and screwed it up. My ego probably got the best of me in this time. The image was otherwise flawless on it. If you could live with the horizontonal collapse it would have made a good monitor. Worth $20 in my opinion. I threw it away to make space for others though.
Mitsubishi AM-3501R- Paid about $15 for it at auction. Big, heavy thing. It's my main monitor and is excellent. The blue gun on it is a bit weak, but you can really only tell that on color test menus. Games look great on it. No burn-in or scratches. Had to take the cover off and turn up the SCREEN setting to make it look really good, before it was a tad dark.
NEC XM-29- Free from an auction. Turned on for five seconds and turned itself off. I looked in the manual and determined it was a cooling fan issue. I blew out the interior with compressed air and it worked. Screen had severe burn in from hospital use, but looked fantastic otherwise. The fan makes a lot of noise.
So there's a lot of variety in the condition and price of this stuff. It's a hobby of it's own. And it's really random. I would as much expect a truckload of NIB XM's as a load of beat up airport monitors.