Hi, Marvin. As Tony said, option 31 is not related to the 31 calculators. In fact it is the multiple pen option for the 4662 - an 8-pen semicircular carousel. How technical is this manual? I have some manuals, somewhere, I think, but I need to know the part number for the little gear that bolts onto the motor spindle in the option 31. (This drives a toothed belt which in turn drives the carousel). This gear on mine is in three pieces (metal hub + two parts of plastic gear). I tried glueing back together, but the thing dropped a tooth on the belt just often enough to be annoying. I suppose I can try again, reassembling the gear more carefully, and tensioning the belt more accurately, but I'd like a new gear anyway... Philip.