Need help w/ Compressor Pump ID

[kams1973]

Came across this pump yesterday, and I am hoping one of the compressor gurus may be able to help me identify the manufacturer. No markings other than casting marks.

 

[kams1973]

OK...a compressor guy tells me this is an obsolete United States Air Compressor Company compressor pump, but he was not sure of the model, possibility of finding parts, etc...Any input would be appreciated.