This was part of my father's (Alphonso Stanonis) system back in the 1980's.  He added a switch (a heavy duty one) in the power cord to turn on and off the power to the computer without having to keep unplugging it.  He also added a pilot LED to indicate that the power is "on" and "off".  Looks like he also added a modification right on the power supply.  Maybe a filter.  I did not take the tape off to see.  I did measure the unloaded output voltage as 11.97 volts.  The pilot light also works.

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