vintage old architectural bakelite Bell Electric Co self-closing wall receptacles/sockets

Lot of two old bakelite electric wall receptacles or sockets. These are self-closing sockets, with spring loaded rotating covers that will automatically close over the terminals when the electric plug is removed. Just insert the prongs of the electric plug, rotate and insert. The direction of rotation is marked with arrows. We're not sure of the exact vintage of these, but are guessing between about 1930 and 1960. One of the receptacles is brown bakelite and the other is off-white or ivory bakelite. They are both marked "Bell Electric Co - Pat. Pend'g - Made in USA" on the backs. The sockets are rated for 125 volts / 15 amp and 250 volts / 10 amps.