I’ve wondered about the strange outlets in my grandparents house since I was a kid.  The house was built in the 60s, back before grounding was a big deal, which explains the lack of a 3rd pin on the outlets, though they are new enough to be polarized.

I was trying to tell someone about these outlets a while back, but I had no idea what they were called.  I tried googling a few things, but about the closest thing I could find is this Leviton model, which is obviously quite  a bit newer.

The back of the outlet unit gives some hints as to it’s origin.  These modules are known as “Sierra Triplex” outlets, and seem to use a slightly modified Decora faceplate.  The outlets are split across two hot buses (two and one, red dot indicates the single), and share a ground contact. All connections are made via side-screw terminals. Electrically, they’re rated for 15 amps at 125vac.

As for other markings, they carry the UL circle, as well as being marked “Made in USA”.  They’re also stamped “Sierra Electric & Mfg Co”.  I checked them out, and they don’t seem to exist anymore, though there are a number of seemingly unrelated businesses called Sierra Electric.

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House, Technology by Kevin