Hi,
Afaik there are two major versions. One is called Focotar and the second is called Focotar-2. The name is on the barrel. The v.1 is quit common the v.2 is said to be much better and is quit rare. Therefore v.2 is much more expensive.
I use a Componon-S 50/2.8 and is as sharp as I could wish for a fraction of the price of the focotar-2.
Cheers,
Michiel Fokkema