I recently acquired a lens set and would like to know more about it. It consists of a brass main body with front and rear threads and an aperture iris that goes from 1 to 6. It has a total of 8 threaded cells, one which appears to be an extension the others are lens elements marked 25, 35, 45, 55, 65, 75 and 85. It is labelled Trousse "Parisienne" No 829.
Any ideas? The focal lengths are puzzling, but I assume there is some matrix of combinations yielding a (large) variety of final focal lengths, as well as f stops.
Any insights are appreciated.