Rare vintage Zeiss/Goerz lens — a pre-war large format optic of historical interest.
The Carl Zeiss Jena 10cm f/9 Goerz-Dagor is a vintage specialty lens element, combining Carl Zeiss Jena production markings with the Dagor (Double Anastigmat Goerz) wide-angle optical formula. The 10cm (100mm) focal length at f/9 suggests a large format, medium format, or enlarger application. No standard 35mm camera mount.
f/9 maximum aperture. 10cm (100mm) focal length. Dagor optical formula. No standard 35mm camera mount — likely a specialty shutter mount or lensboard configuration for large format or enlarger use.
The Dagor formula is a classical double-anastigmat design originally developed by C.P. Goerz and widely copied by German manufacturers. At f/9 and 100mm this is likely a specialty lens for large format field cameras (mounted in Copal/Compur shutter on a lensboard) or an enlarger lens. Very slow aperture for normal photographic use.
On the used market this is a specialty vintage optical element. Condition checks: element clarity for haze, fungus, or separation (typical in 50+ year old glass), aperture blade condition, shutter operation if applicable. No standard 35mm camera mount — requires large format lensboard or specialty adapter for any modern camera use.