For instance, of the four lenses Donald named, the Dagor is a Goerz lens with six elements in two groups on which the Schneider Angulon is based (not the Super-Angulon or any of the later ones, though). The Goerz Apo-Artar is the model for the Rodenstock Apo-Ronar. Sironar originally referred to Rodenstock lenses that were very similar to the Schneider Symmar. Any lens made by Nippon Kogaku is a Nikkor of some sort or another, regardless of design. The earlier Nikkors had a letter indicating the number of elements, so a Nikkor-Q (quarto) was a 4-element lens, probably a tessar, and a Nikkor-O (octo) was probably a complex 8-element retrofocus wideangle lens.