Bump. I've spent some time with the keyboards and it seems the older ones respond more slowly over the USB converter than the ones with a new purple PS/2 plug. I think I've noticed some transpositions too. They have a different feel than the newer units, more friction, I think, and more tactile, definitely more noticeable actuation, definitely more ping but maybe less smooth (and less interesting to type on), it feels like typing on the desk itself. Hard to tell the exact parameters, though. The '96 one feels different from the one from '95, which actually has a speaker. At the same time, all 10 units seem to have the same black alps on the exterior, the weight of the keyboards also seems to be the same.