James, Good one. I had to Google it and re-read the posts but then again I am just a castaway.
There are two ways to do this: The first is to measure the dipstick AND the dipstick tube. My M-130(280SL) dipstick tube is almost exactly 16" from the oil pan to the top of the tube. The stick is 18-3/4" and 20" from the underside of the hilt where if meets the dipstick tube to the High and Low lever marks respectively.
The second is to do an oil change adding the listed capacity of oil, start the engine to fill the filter, shut it off and compare the oil level on the dipstick to the level marks.