I looked for QEDS on Agilent site for quite a while but the only info I found was an old HP memo that this particular part number (and many other) is discontinued. (the encoder in question is old, it was produced by HP) - Unfortunately no parts with number 9864 and 5956 were found, I tried 9800 and 5900, one of the "classes" seems to be reserved for alignment tools, the other doesn't turn up in "motion control" class at all. I found parts that LOOK similar though. That at least gives hope that the pinouts remained unchanged.