GR874 connector
The designation GR874 for the RF connector refers to the development company General Radio.
The GR874, also referred to as the G874, is a hermaphroditic microwave connector whose frequency range extends to 8.5 GHz. The impedance is 50 ohms, as with all other RF connectors.
When the two sexless connectors are mated, the four mating contacts of the outer ring are pushed over each other to provide RF leakage. The GR874 connector is extremely robust, but is no longer used in new devices.