US collector and Japanese anthropologist Frederick Starr was a turn-of-the-century collector and avid participant in or (votive slip exchange clubs), so much so that he was given the name "Dr. Ofuda". He collected tens of thousands of slips, and a fellow collector and popular art enthusiast, Gertrude Bass Warner, purchased much of his collection. It currently resides at the University of Oregon Knight Library Special Collections & University Archives, part of the Gertrude Bass Warner Collection, and examples are viewable online at UO Oregon Digital.