Raimey, thanks for your detective work. I don't have the gun in hand, yet, so hopefully I can find out more when it comes. I don't know where the seller got Stadelmann name from, but did see a similar mechanism with the Stadelmann name in a Nitro Express post. Yes, from a visual standpoint, it does resemble a Bastien. That little gizmo on the left that you asked about ? Could it be a snuff box ?
Here a thread with a Stadelmann if you scroll down a long way.
http://forums.nitroexpress.com/prin...=paradox&main=251424&type=thread