Leitz's vintage Elmar 90mm for screw mount — the uncoupled telephoto with E39 fitting.
The Leitz Elmar 90mm f/4 with E39 filter thread in an uncoupled configuration is a telephoto prime from Leitz for Leica Thread Mount (M39/LTM) cameras. The 'uncoupled' designation indicates this example lacks rangefinder coupling — it must be focus-estimated or used with a separate viewfinder.
The lens delivers 90mm at f/4 maximum aperture in Leica Thread Mount (M39) with an E39 filter thread, manual focus via the focus ring without rangefinder cam coupling, and full-frame 35mm coverage. The Elmar designation covers various Leitz lens designs across the company's history.
The uncoupled Elmar 90mm was used on early Leica cameras with the VIDOM or FIKUS viewfinder accessories rather than rangefinder coupling. Today it can be adapted to Leica M via an LTM-M adapter but focusing accuracy depends on using the distance scale rather than rangefinder coupling. The lens itself is optically functional.
Verify the uncoupled status — the rangefinder cam may be present but incorrectly calibrated, or absent entirely. Check the LTM thread for clean engagement. Inspect the E39 filter thread. Test aperture blade operation and element clarity. For M body use, an LTM-to-M adapter enables direct mounting with distance-scale focus.