If I recall, only the Venture Royales had the Class system on them. I also think that by 1988, you could only get the Venture Royale and not just a Venture. The Royales came with the Class and radio system on them. So first question is on the side bags, do you seem a emblem that says Royale on them or anywhere else on the bike?
I am thinking the previous owner removed the compressor and control valves from the bike. I can see the mounting legs that held the plate with the assemble on the bike under the front part of the rear rack. So people have converted the Class to the non-Class system which is a schrader air valve that is usually located on the left side of the bike where you can adjust the damping for the rear air shock. The also place one up near the center of the forks to adjust the air there. You might have to do some searching for them and see if you can find some black air hoses that use to run to the back of the bike on the right upper side of the frame. I think the previous owner left the controler in the fairing just so he wouldnt have a hole to fill.
Good luck and keep up the good work.
Rick F.