I'm sorry, I'm just not fully understanding your description of the attachments. Are they the same device H-D has used forever on hard shell bags ? I ask because the Road King Classic uses the same hardware to attach the leather bags as is used for the hard bags. The only difference is the distance between the holes is wider on the leather bags and you have to adjust the clip section of the two piece fastener accordingly. Anyway, if that's what was used, the pins on these pieces have a groove in them that when you twist the pin pulls the bag into the fastener tighly and locks it. So to release, you push in and turn counter clockwise. To attach you push in and turn clockwise. Not sure if I'm just blowing smoke here cause I really don't know what you've got but it sort of sounds like you might have these. The mount to most H-D's easily with just one 7/16" fine thread (ASE) bolt. They have a name and damned if I can remember it but they are also used by car racers for attaching body panels to frames so they can be removed quickly.
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