Canon's generic 70-210mm f/4 — likely EF or FD mount constant f/4 telephoto zoom.
The Canon 70-210mm f/4 without specific mount designation could be the EF (ID 934) or FD (ID 1762) version. The constant f/4 telephoto existed in both mount systems. Verify the specific mount on any purchase.
Constant f/4 aperture throughout 70-210mm — the distinguishing feature over variable-aperture consumer alternatives regardless of mount version. Check for EF or FD designation to determine compatibility.
Mount must be verified — EF (ID 934) provides autofocus on Canon EOS, FD (ID 1762) is manual focus on film SLRs and mirrorless adapters. Both provide constant f/4.
Check against IDs 934 (EF) and 1762 (FD) for mount-specific details. Available used very cheaply. The constant f/4 is the main appeal regardless of mount.