Review on Enhanced Safety with COOPER WIRING 3Wire Duplex Recpt: A Reliable Power Solution by Michael Boyce

Before polarized plugs became popular, these surface mount outlets were a popular way to add an extra outlet in a convenient location. These days they are almost impossible to find in a hardware store. To install it, you need to be sure you've connected it correctly (if you don't know how to do it, there's a 50/50 chance you'll get reverse polarity). Perhaps that is why they are not available for DIY enthusiasts.