As shown it is correct. 2,3,5 on the left: 1,4,6 on the right. it's one of the odder -11 backplanes. I believe the reson for that odd layout is when cascading multiple boxes (BA11M) the cables orient easier as option 5 to next box topleft is the shown configuration and the REV-11 prom boot is nominally in option6 as bus grant continuity is not required for most memories. My source was the Microcomputer handbook 1976/77. I also have one with core in it. Allison