IEC 60169-8 Amd.1 Ed. 1.0 b:1996

Amendment 1 – Radio-frequency connectors. Part 8: R.F. coaxial connectors with inner diameter of outer conductor 6.5 mm (0.256 in) with bayonet lock – Characteristic impedance 50 ohms (Type BNC)
Amendment by International Electrotechnical Commission, 03/13/1996