A photograph of Orenburg Cossacks about 1916. Note the caps are softened and the shoulderboards largely sewn. I don't think these men are cavalry, noting there are no swords and the men largely wear puttees.
Definitely cavalry this time! Some men appear to have coloured cap bands, but the lack of any shoulderboards and what appears to be a banner to the left suggest they might be Soviet forces or partisans.
Allegedly a photo of RCW era Orenburg partisans. These men are ethnic Tatars, who had long been part of the Orenburg Host.
Nagaybak Tatars. They are basically identical to normal Orenburg soldiers. A few men had Asiatic features, but not very strongly. Supposedly taken in 1916, but the uniforms, with the stiff caps and hard shoulderboards suggests earlier.
Orenburg officers from 1919. Note the fancy gymnastërka with piping (a type of ermakovka) of the man at the back. The man on the right wears the equivalent type in khaki, which seems to have been a favoured local style.
It's unusual to see men of the period bareheaded in posed photos, but some are in the previous photos as well.
Typical officer, presumably WWI era. Note the wide trouser stripes. Unusually for a Cossack, he has spurs.