560SEL Rear Levelling Reservior

What does the rear, self-levelling reservoir look like when full? Is there a mark on the plastic that indicates full that I don't see? My rear rides high, Actuators were replaced just before I bought the car in August. But the levelling doesn't adjust. I have to get under the rear and play with the lever, but i don't even know what the level looks like when full. Help!