ECN Forum Forums Code Related Discussion NEC & other Code issues SquareD XO series?????

I saw a panel in an old church the other day that was a Square D XO series. Has anyone ever heard of this line? It appeared to be another one of SquareD's proprietary systems, and it didnt look like anything available today would fit. Should this one be disconnected and trashed?

BTW, there was a small 2 cicuit 30 amp cicuit breaker disconnect panel for a water heater next to the XO panel made by............yup, you guessed it, FPE!!!

IIRC, the bus position on single-pole XOs was determined by the direction the breaker plugged in. I think they are a mid-1950s vintage, and the Cutler Hammer version was interchangeadle with Square-D.