, originally uploaded by *jj*.
I can use my M42 to AR (Konica) adapter to affix the new ancient and dirty East German CZ Jena unbadged "Biotar" 58mm f2 lens to my Nikon D40. It kind of fits but I was to scared to turn the AR adapter on the D40 until it clicked. But it was light tight nonetheless.
The Biotar has bubbles, black flecks and dry grease. The Tessar, however, is perfect and mostly lives behind a Rollei 30.5mm UV filter.