Yours is likely an old CR Brakemaster unit, basic design is the same on the SKF but the SKF has been updated with a heater.  Like I said, I didn't have much to do with the one kicking around the shop, cause all our stuff at the time used the European design unloaders. All my stuff today runs Bendix AD-4's. 

Last one . Thank you.

One more.

Hopefully this picture can help with anymore info?

Thank you all again for the responses. 
Tundra provided the information that enabled me to google some information, info that has since been provided by others. The closest mine comes to any of SKF description is the Turbo AC. Except my example does not have the 12/24 volt heating element option. It is cast over.
Without the electrical option, the example I have seems to match up more with the Brake master model 62 or Mt 23508. 
Plumbing? My best estimate ( it was a 105* last week) top port is the outlet to the wet tank. Lower section has three ports. One is 1/4 inch for the governor, the other side inlet from the air compressor. Directly out the bottom is the exhaust port.
I have it disassembled and will post some pictures shortly.

Yeah, it was originally a CR design. I remember one at the bus company back in the 80's I don't know who bought it, but they will not work with the European design compressor systems, where the unloader is in the outlet line and just dumps the compressor output. It sat in the store-room the whole time I was there.  

Thanks, Geoff. That explains it all. Leave it to JOT.

And tundra probably was correct. CR, Chicago Rawhide, is now part of SKF. 


Tony

I was wrong, called the "brakemaster" Turbo- AC and is shown in this PDF.
https://www.skf.com/binary/86-147914/457969.pdf

Very unusual compression coupling.


What size are the fittings and how many ports were used? Looks to be a steel shell with a cast iron fined end. Maybe it was for a high pressure application and not original to the truck.


Tony

Me thinks you are right, was it call "Pure-air?" I just can't clear the cobwebs from that part of my brain.