It hasn't much value, except as a desirable 'collectible' display piece.
What you have is a high quality two-stage compressor, of (probably) late 1930's vintage, with a single phase 'repulsion-induction' motor.
It could be set for 150 to 175 lbs. of air, when it was new.
The 'catch' is that any old air tank is a 'gambling device'. Sometimes, they will have rusted inside, on the bottom, to a point at which the tank may rupture violently when under pressure.
You can find stories of such tank 'explosions' on the internet. They are not all that common, sometimes old tanks simply rust through in 'pits' or 'pin-holes' and become 'leakers'.....but a violent tank rupture is a very serious incident, when/if it were to happen.
That pump is high quality, and may work well. Its only draw-back is that maintenence parts are almost certainly not available, particularly valve discs and springs. I don't know whether Champion is still in business, but it couldn't hurt to find out. If they are, I'd strongly suspect that they no longer supply parts, but I could be mistaken.
Those old R-I motors will 'run on forever' if the bearings are kept oiled and brushes replaced as needed, which they seldom are.
You could, indeed, fit that compressor and motor to a new, or late production, tank, and, if the unit runs well for now, it may work well for you in the 'intermittent duty' of a 'hobby shop' application.
I'd suspect that, if it were diasssembled, given a really nice refinish, or 'aesthetic restoration', some collector of old gas station equipment would be very seriously interested in that unit for display. If so, ask for a best-quality, more modern, compressor, such as a Quincy, or Saylor-Beall, in trade.
Just don't risk having that old tank up to pressure.....it *may* be sound, but the risk of dangerous failure is not worth it.
cheers
Carla