I recently came across a house that was slated for demo that had the SqD "XO" type panel. It was the 20 space veriety... all in a single column, with each breaker installed in a left/right alternating arrangement. I estimate the house to have been built in the 1910's or 20's. The house was wired with knob & tube, but the panel had mostly paper-style NM cable entering it.
I gather this panel type is newer than the house... probably replacing an older fuse panel as part of a rewire job.
When did the XO panels appear? When did they become obsolete?
