Well, that's a single stage Aquatek regulator with a preset working pressure. New, it costs maybe $75 shipped. And you're right, that looks more like a 10lb tank. This just became a realistic deal.
Assuming the Aquatek is functional, I'd probably pay $40-50 shipped if I were in desperate need of a used rig. The 10lb tank, however, is still worth some cash. Not quite $110, but getting close. Figure $80-90 maybe.
So ....if it were me, I'd probably buy the whole thing, sell the Aquatek rig for $40, and have just spent $70 on a 10lb tank, which is a good deal.
If you're looking for your first CO2 setup, and you're willing to go with a used rig, $110 is still a very good price for everything you need. Again, assuming it works.
NOTE: Aquatek is not a "good" brand. It's cheap. Which may be exactly what you want to get into CO2. Up to you.