Some of the Russian (Soviet) lenses have amazing glass... there are stories that when they invaded Germany and took over Zeiss that a great deal of zeiss glass was used in their early lenses... especailly at the KMZ factory... so the earlier the serial number the better... also, there are tales online that the lowest numbers were reserved for party members and special care was used to select the best performing lenses. In any case, many interesting lenses... I have several (MTO-1100A, Tair 11a, Tair 37A, Jupiter 11A, helios). It is worth mentioning that several of the lenses like the Jupiter, Tair, MTO and Mir have the letter "A" following the model number. These are awesome because the attachment can be removed and replaced to fit different camera makes without worries of losing infinity focus etc... there are adapters for Nikon for example.. they are called KP-A/N adapters.. You juet remove 3 set screws and the old mount comes off and the new one goes on... it's brilliant... Also some of the old Helios and Tair lenses have different numbers of blades (6, 8, 13, 16, 20). This is cool because it seriously impacts the Bekoh... I bought my lenses about a year ago but then life took over and I never really got an opportunity to play with them... this thread reminds me that I need to get back to that!!!