An interesting early Carl Zeiss Jena Tessar lens with a later modification to allow it to fit to M39 (Leica screw thread cameras). It could obviously be adapted to M42 via a M39 to M42 ring.
Please note that the lens does NOT have an iris/diaphragm.
The lens is fitted to what appears to be a home-made tube that has a focusing helicoid (with distances engraved on the tube).
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