Steinheil's fast Exakta normal — the double-Gauss Auto-Quinon 55mm f/1.9 standard prime.
The Steinheil Auto-Quinon 55mm f/1.9 is a fast standard prime from the West German maker Steinheil München, offered in the Exakta bayonet. Steinheil was a long-established optical firm whose Quinon line supplied bright normal lenses for several reflex systems. The Auto-Quinon served as the fast standard for Exakta bodies as a West German alternative to the East German glass.
This is a manual-focus Exakta-mount lens with a 55mm focal length and a maximum aperture of f/1.9. It uses a double-Gauss standard optical layout, the Quinon type. The aperture is set on the barrel and, as the auto in the name indicates, coupled through the Exakta automatic stop-down mechanism. Element count, filter thread and weight are omitted here where they cannot be confirmed for the specific Exakta build.
The Auto-Quinon 55mm gives a bright viewfinder and shallow depth of field wide open, with central sharpness that builds on stopping down and smooth out-of-focus rendering. It is a flexible fast standard for portraits at head-and-shoulders distance, street work and low-light general shooting. Its West German rendering is a slightly different flavour from the more common East German normals of the period.
Used Steinheil Auto-Quinon lenses appear less often than the East German standards, so expect to search. Inspect the glass for haze, fungus and separation, and confirm the aperture blades are dry and the auto mechanism works. Check coatings for cleaning marks and test the focus for smoothness. On mirrorless via an Exakta adapter it makes a capable, less common vintage fast normal.