Tunnel terminals were once fairly common for switches (rarely for sockets) but were replaced by compression plate terminals by the mid 1960s. Sockets mostly had simple screw terminals, better versions with guards on either side of the screw so the wire can't slip out without bending a hook or better ones compression plate. Both versions were in use until the 1980s when push-in terminals became popular and eventually replaced all screw terminals.
As far as I know none of those terminals ever fit more than 2 wires of any cross section properly... some people did manage to squeeze in 4 1.5mm2, but they're only listed for 2.
