Pin & sleeve connectors
A line of heavy-duty pin & sleeve wiring devices that conforms to UL1686C-1 is explained in a 12-p brochure. (The UL standard provides for interchangeable electrical connections between the products of various manufacturers.) The receptacles, plugs, and connectors described offer complete interchangeability, including mixing of metallic and nonmetallic parts.
Hubbell Wiring Device – Kellems