David,
the JAN specs where designed by the government with several manufacturers producing the machine. There where some modifications.....one by Ampro had a Gevena pull down sprocket run by a "drunken screw" cam ( like Norelco / Kinoton ). Them unit was rock steady with shutter drive and movement in a easily replaceable oil tank. This unit did not output as much light as the claw type drives and where more expensive to manufacture; so examples are rare. I worked at a T.V. station in the late 1960's where we had two of these chugging along reviewing prints for broadcast.