Without an aperture, it was meant to be used at a specific distance and magnification -- as Matt said, a "machine printer", such as a "mini-lab", traffic control camera????. The list is endless. From what little I can tell from the lettering, I'm thinking "Soviet", but I can't tell. Just because the box says "LENS UNIT 43" does not mean it is a 43mm lens. For all we know, that might mean it was produced at Gulag 43. What can you tell us about the seller? Age of the lens? Date on the box??? Any crumb of info????