The repeating action on this is unique. A sliding cone over the muzzle was driven forward by the muzzle blast. A long rod connected to the cone worked a lever that unlocked the breach. Søren Bang had been working on the design since 1901, and this actually passed field trials despite being less than robust and susceptible to failure from the corrosive primers, which weakened the cone.
I want one just because of the name. Yeah, I know - I need to grow up. Not going to happen.