I was leafing through an old The Conjurer's Magazine and came across this ad:
I briefly looked up John J. McManus. He was quite a collector who left his enormous collection to the Library of Congress. According to the NY Times, he was also the American rep for Rolls Royce and an owner of the Hudson River Navigation Company. Therefore, I suspect that the 10 grand challenge was quite legit. (That's the equivalent of over $93,000 in 2011 US dollars)
Does anyone know if John Mulholland took up the challenge?