We have 2 Electric Duplex Outlet ornate design NOS Vintage items in the original package - They are considered a duplex outlet and are labeled  15 S 125 V.  They come from an estate in CT where the woman tested/quality control from an electrical supply company.  I would estimate that they date somewhere between the 1940's - 1960's or so.  Around each outlet/plug there is a decorative design on the outer edge.  The outlet plugs measure about 1 1/4" in W x 1 1/8" in L.  Upon initial listing I have a few available which are identical.  They are new in the original wrap.  This one is a deep brown, almost black.