The power director [shuttle on yours] fill/dipstick screws straight down into the top left side of the housing, just to the rear of the dash, on my D15 II farm tractor. It's longer than what you show, and has a hex, bolt type head, not the big breather you show.
Over on the right side of the tractor, under the fuel tank, going into the torque tube at an angle, is a filler/dip stick just like the one you show. It's for the tractor hydraulic system. I assume that's where yours is. Yours simply indicates the oil level for a tractor with no hydraulic system there.