This is Eugene Burger's special coin clip, custom made by Robert Charles, for use in performing "The Four Coin Opener" as explained in Teaching Magic (2017) and "The Three Coin Mystery" as taught in Eugene's Real Secrets of Close-Up Magic video from 1991.
Teaching Magic: A Book for Students and Teachers of the Art by Eugene Burger, with additional material by Lawrence Hass, Ph.D.
Eugene Burger's "The Paper Hat Mystery" Performance Kit (including video)
Eugene Burger's Bonnet Style refills
Eugene Burger's Stocking Cap refllls