What kind of an engine is this

[gt2ride]

I stopped for a tour of a copper mine south of Tucson AZ. I took a pic. of this Eng. thinking it would be a good project. I am not sure how it works. I think it is a combination pump eng assy. Has anybody seen an Eng. like this. The flywheel is 4ft dia. and the bore is 12in. There is two section to this Eng. both have a 4in pipe going in and out.

 

[cfellows]

Can't see if there is a cam or valve arrangement on the far side. Looks more to me like just a dual chambered pump or compressor. Just a guess.

Chuck