The “Olympus OM Zuiko Auto-Macro 1:3.5 f=50mm” introduced in 1973 was the first version of this lens, it was single coated. The second version “OM Zuiko MC Auto-Macro 1:3.5 f=50mm” followed and was multi coated. This third and final version is the “Olympus OM Zuiko Auto-Macro 50mm 1:3.5” Through its three versions the lens was produced from 1973 to 2002. Excellent build quality & style & quite similar to the Pentax 50mm macro. I haven’t decided which of the two I prefer yet!