It was also called the ‘Muff Pistol’ or ‘Pocket Pistol,’” Tulsa police posted to social media on December 8. “This pistol is something a bit different and somewhat rarer; this is an ‘underhammer’ pistol,” said Helms. Underhammer guns aren’t traceable to a single person or era, but firearm historians do credit its popularization to Nicanor Kendall. “It looks like a Bacon & Co. Underhammer Pistol,” she tells Popular Science. “All the same, this is an interesting antique pistol,” Helms conceded.