According to the doc the "optics" encoders appear to be quadrature encoders. This tutorial shows an encoder knob that is functionally and electrically equivalent to what you have.
The picture of that robot is pretty poor, but from the look of things, those motors appear to be Pittman DC motors, with encoders. Have you tried contacting the current manufacturer of these motors (whomever they are) for datasheet info (and hookup info for the encoders)? If they are Pittman, contact info here:http://www.ametek.com/locations/pittman-location.aspxNote - be nice, state what you are wanting in plain language, offer to pay for the information (literature shouldn't be too expensive - but I can tell you that the gears in those motors are not cheap, so don't break them!).