Tinker,
I think what you have is a 'dual fire' gun - pinfire and percussion. I have asked Steve Nash to post a couple of pictures for me. I'll bet your gun either has no ramrod or one that is too short to be of use and/or is not designed to accept cleaning accessories. If so, it was intended to be a 'dead weight' to knock out the percussion cartridges. My Berringer has a trap in the butt for the percussion cartridges. One of my photos will explain how the removable sliding pieces in the standing breech work with the percussion cartridges.
Steve