IBM 029 card punch

Hi, I have here three IBM 029 card punches, two model A and one model C (with interpreter) including documentation. So far so good. I do have an additional 029 (I *think*) without covers which I would like to restore. The problem is that it is "a bit" different from the other three punches and I would like to know what model this is and if anyone has the maintenance manual for it. The mechanical part is almost the same as in the A and C models, but the keyboard has two lights, one at each side. I know that the light on the left side is an indicator for the verifier, but the one on the right side is unknown to me. It is a printing punch and has two program drums each with 12 star wheel contacts (instead of the usual 8 on the front drum). Now comes the electrical part: It is very different from the other three punches. It has more SMS cards (about 12, not including the cable cards) and many more wire relays (no reed relays and no electronic components except for some diodes, resistors and capacitors). But the most interesting feature of this unit is the "I/O" port on the rear left side. Does this ring a bell to anyone? Thanks, Christian