Sharptail, the top rib is kind of interesting. I haven't seen another one that works the same way. It's like a reverse dollshead. When you push the top lever to the side, it pulls back the section of the top rib on the receiver that (when the gun is closed) otherwise fits into a section on the barrel. The other thing that both my gunsmith and I found interesting is that it needs to be snapped closed. Carefully closing the gun doesn't work. It kind of goes against my grain but we're convinced that the way it is supposed to be done.
I wish I knew more about the gun's provenence but the guy I bought it from could tell me remarkably little. On both this gun and the Hyem I feel like I took a gamble and ended up with a fantastic gun. My gunsmith, who works on the best....Purdys, etc., tells me that while the wood is nice but nothing special, the barrels and action/locks on this Pieper are as well crafted as anything he has ever seen. And he thinks the only good guns are made in England.