Quote Originally Posted by shutterfinger View Post
A Lens Collectors Vade Mecum shows that Xenar is a trade name applied to a Tessar design (http://en.wikipedia.org/wiki/Tessar), which has been produced since the early 1900's and that SC is a reversed element tessar layout.
Not all Xenar lenses are Tessar design there was a fast f2.8 5 element Xenar introduced around 1935, the VM mentions a 1939 BJA paragraph on the Xenar but overlooks the earlier 1936 entry introducing the lens.