it is an doppel-anastigmat f.6.8, (4 in 4 groups) [I] took it apart to clean it...it looks to me very clean no fungus, If I will be able to bult this adapter I want to replace the old lens with the Yamasaki C-CONGO 1:6.3 f=150 on it, it is in very good condition and I think it will fitt the camera and it is much better IMO