I’ve a barrel mounted convertible lens that has been identified by Schneider as a 180mm Symmar from the 1960s.
However, I’m confused over the two sets of aperture numbers on opposite sides of the ‘iris ring’.

With the front lens cells fitted the aperture set of
5.6 8 11 16 22 32 45 is used
Is used whereas with the front lens cell removed the aperture set of
12 16 22 32 45 is used

My question is why, when there are seven click stops on the iris ring, do I only get five aperture settings when the lens is in its ‘converted’ mode?
Regards
Tony