Thanks, Steve. I knew that someone would have info. I knew that it has good wideangle coverage, but the ability to use front, rear or both is a pleasant surprise. When I cleaned it I thought it looked nearly symmetrical, but I did not know it is a "convertible" lens design. Now I will need to measure the iris at the various stops to determine correct f stops when using the cells separately.
I just found a German website that lists the Heli-Orthar as a higher quality lens by Plaubel. I will try to set up a lens test target to check the resolution this weekend.