I print for Markéta Luskačová who is another great Czech photographer from Prague and a contemporary of, and good friend of Josef Koudelka. I remember her telling me about her and Josef often buying cuts of motion picture stock from a Prague cameraman. This was actually illegal, as the film company was State owned under communism, but was a way for the cameraman to make something on the side and for young photographers to get film cheaply. However, they never really knew what they were getting and if it was fresh stock or something years old and found in a cupboard. Often it was in an unmarked tin, so no clue until processed what film it was. I think they used to share a darkroom, but both had left Czechoslovakia (as was) by the mid 70s. My impression of the images originally posted is as others said, probably copies of prints on lith or line film and greatly enlarged. Will have to ask Markéta next time I see her. She always has great and fascinating stories!