Oil pressure question on a 1919 Super Six

Unknown

The question is, what is the oil pressure supposed to be on a 1919

Super Six? The one that I rebuilt a couple of years ago is registering

55 psi on the guage and it has sat for a couple of weeks getting new

tubes in the tires and when it fired up he said that the pressure is at

55 with no change in engine speed. When I rebuilt the engine the

original guage was still in use and was right on with a new direct

reading guage. My initial thought would be to put another direct

reading guage on and see if it is the guage or not. Another thought

could be the regulator valve. Any help would be appreciated.

Mike