Quincy 216 ROC 19 questions

[GSinILL]

I am pretty much a newbie when it comes to air compressors.
Picked up an old compressor with a Quincy 216 ROC 19 pump.
Seller said it was running and working not too long ago.
What I am wondering though is why there is a gizmo (unloader?) on the shaft opposite to the pulley that is not connected at all.
I would have assumed that the copper pipe that is connected to the top of the pump head should be hooked up to this somehow?
First pic in the attachment shows the pump and the second one how the copper pipe is run; the 3rd one the connection to another valve/switch at the pressure gauge.

It needs some work before I can run it and I would like to make sure I have it hooked up correctly before starting it up for the first time.

Any help/link to the proper hook up would be appreciated.

Cheers
GS

 

[The Cobbler]

it looks like the centrifugal unloader ( at the crankshaft) was going to be replaced by an unloader on the pressure switch

 

[GSinILL]

Thanks, so should I be able to just reconnect the one on the crank shaft?
And how would I have to hook it up?

 

[The Cobbler]

I don't know alot about the centrifugal unloaders, but it is possible it went bad thus why it's been removed.