I don't see many with utility beds, especially in any color other than white. I think it was probably installed when new, which would explain why they went with the Camper Special package (although I'm not sure how different a C20 CS is than a C30 SRW). Of course, whoever installed it decided to weld it to the frame...
The seat I have is from a Suburban (I think), so it doesn't tilt. Don't think I've seen that in a pickup before, and it sure makes getting the motorcycle ramp in/out of there fun.