I have recently come to possess a Horseman monorail 4x5 camera and I don't know what model it is. There is no model ID to be found anywhere on the rail, standar ds, or anywhere else. I do know that it was probably purchased new about 10-15 y ears ago. It does not have the yaw-free feature I see on newer models. All move ments seem to have adjusters with tightening feature. What else.... it's black. It's not with me or so I can't include the serial number. I'm pretty sure it's an "L" model but I understand there are several and would like to know more. Any help?