old heavy solid brass Gresen hydraulic gear pump for tractor or farm machinery

Vintage solid brass hydraulic or oil pump from an old farm estate. This is a gear pump design with heavy cast and machined brass housing and steel drive shaft. It is marked "Gresen Mfg - Minneapolis". The pump inlet and outflow ports have thread in male adaptors for standard garden hose threads, so we think that this pump was being used with water, but we're not sure and were told that it is a hydraulic pump.

The driveshaft is about 5/8" across and the pump measures about 5" long, 5" across and 6" deep over the shaft. This has a patina of age to the brass.