As far as I know, we cannot speak of true "cossack saber", as they were part of a larger area and have adopted the arms found wherever they were. I think our friend Wolviex can elaborate.
Janusz, great site. I wrote a short essay myself about the navaja, alas I'm afraid automatic translator do not work well with Hebrew...
http://www.collect.co.il/content.aspx?id=187