1956 NEC
4156. LAMPHOLDERS,SCREW-SHELL TYPE. Lampholders of the screw-shell type shall be installed for use as lampholders only.
At one time, wall-mounted 'receptacles' for serving portable appliances had traditional edison-base screw shells. You could literally screw a lamp into a wall-mounted receptacle. The one I have seen in an older house had a brass, hinged cover to save unintentionally contacting live conductors.
