Klass made this offer openly to anyone. The offer was specifically declined by Frank Edwards, John G. Fuller, J. Allen Hynek, and James Harder, some of whom were the most vocal promoters of the extraterrestrial hypothesis. One person entered into the agreement with Klass. A man in Seattle, Washington, accepted the terms in 1969 and made two annual payments of $100. Then in 1971 he wrongly claimed the prize. When it was pointed out that his claim didn't meet any of the conditions, the man let the agreement lapse. In his book "UFOs Explained", Klass offered to refund the full purchase price to every reader of the book if any of the conditions of his "UFO challenge" were ever met.