Judging by some of the artifacts i saw in the images i'm not even sure it was film. I think it may have been glass plates that were used for these. In a few there are areas where it looks like the substrate had flaked off of the negative when they made the positives.

Given that wikipedia says that film was starting to take over around this era I'd say that it's quite possible that it was all photographic plates since to do this well with something you'd have to have a good amount of experience with it and I wonder how much film and the processing would have reached Russia yet by then.