As Fred Nelson shuffled through a crowded convention center in Tulsa, Oklahoma, a man tapped him on the shoulder to ask about a gun.
The man knew Nelson was selling thanks to the handwritten menu taped on Nelson's backpack advertising more than a dozen handguns, rifles and shotguns.
He offered $300 for a Glock 19 pistol listed at $350.
"Meet me in the middle at $325," Nelson responded. "It's never been fired. You can look down the barrel."