I saw that Cabelas is selling what used to be the Ardesa derringer, now the Traditions vest pocket derringer. I googled some videos of these guns and came upon one of those videos that make me cringe. The part where he caps the gun.
https://www.youtube.com/watch?v=-fck54fGGH4
https://www.youtube.com/watch?v=-fck54fGGH4