I've been experimenting how to make breather cards. And someone made reference to a "Pinch card", a creation of Scarne. But I have never been able to find any information about it. Can someone point me in the right direction?

For this, Scarne used a unique type of crimp—a cross between the Will Deceive coin impression described by John Northern Hilliard in Greater Magic (1938) and a breather crimp: Ray says that Scarne called it “The Pinch.”

Remove the four Aces from your deck and get a dime with a nice milled edge. Your left hand holds one Ace vertically, with its back to the right. Your right hand holds the dime vertically, so its milled edge is at the center of the Ace’s back side. Press the edge of the dime against the centerof the Ace, while your left thumb and fingers give the dime a pinch through the pasteboard. Repeat this with all four Aces.The pinch/crimp will be much too large at first, so insert the Aces into different parts of the deck and shuffle it thor-oughly, working the pinch down so it’s just barely there. The break it creates that allows you to cut to it is not visible when looking at the side of the squared deck—it is something that can only be felt after much practice.