Hi Paul,I think this may be a Divers air pump, what do you think? Brian in Mooroolbark.

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id3-p1

I suggested it might be an amonia pump from a cool store, but Brian responded:

Hi Paul,Not amonia pump,Has 38" flywheel,no intake valve, it breathes through 8 1/2"holes in cyl. wall when the piston is at the end of the stroke. air is pumped through the copper coil which is water cooled. It has been sugested that I turn it into a hot air eng.Brian