gravely model d cam shaft

Hi there i need to find out about oil pumps on my gravely ..... there is a wobble oil pump that operates off the cam shaft but there is also an oil pump that operates off the other side of the cam shaft ,,,,,,, the cam shaft has no lug fitted to run the wobble pump and by the look of it there has never been one fitted and there is no where to fit one to although there is one shown in the parts diagram ,,,,so was the external pump on the other side a modifaction and is the wobble pump redundent
thanks for reading this
pete