Zeiss's generic 135mm f/3.5 — likely a Jena or West German telephoto without specific designation.
The Zeiss 135mm f/3.5 without specific designation may be from Carl Zeiss Jena (East German) or Carl Zeiss Oberkochen (West German) — the Cold War split produced two separate Zeiss companies making different lens versions.
Optically good — Zeiss quality at 135mm f/3.5 regardless of specific origin. The 135mm provides useful telephoto reach for portraits. Various mount versions exist. The Zeiss name guarantees optical quality.
Mount and origin must be verified — could be M42, Contax, or various other mounts. Zeiss quality regardless of origin. The 135mm f/3.5 was a common telephoto specification across many systems.
Available used very cheaply. Check specific origin (Jena vs Oberkochen) and mount type. The Zeiss quality is genuine regardless. For vintage telephoto needs. See ID 2034 for the Jena DDR version.