I was rearranging stuff in my basement and found a strange looking receptacle. It is on a 15A circuit in an 1950s house. It is in a room that I suspect (for a bunch of reasons) was finished by the owner rather than the builder, probably in the 1960s or 1970s.
Best Answer
It's a plug that accepts Hubbell's 1906 tandem and 1912(?) parallel plugs. Both were rated for a maximum of 250v, but usually wired for 120.
Similar rating to Edison 1" (now called E26), most are rated for up to 250v, but we commonly see them used only for 120v.