While the 127mm Ysarex is lauded by many, it is a single-coated lens.
There was a later 135/4.5 Ysarex which is multi-coated. (There may also have been a 150mm version.)
I have one. Performs beautifully. It is a quality optic which does not disappoint.
I like it better than the Fujinon 125mm and 135mm lenses that I have had in the past.
It is a Tessar design so it is also a light-weight lens.