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Copio de la entrada de Erdnase (y pido disculpas porque esté en inglés. Ni maldita gana que tengo de traducirlo):

Identity
S. W. Erdnase was most likely a way for the author to conceal his real identity so he wouldn't be arrested but so that people could figure out his real identity later. S. W. Erdnase spelled backwards is "E. S. Andrews" leading many investigators to search for people named Andrews as possible candidates.
Milton Franklin Andrews

Martin Gardner has proposed that a small-time con man named Milton Franklin Andrews was the author. Others argue against Andrews being Erdnase because the known examples of his writing are very much inferior to the polished writing of The Expert at the Card Table.
Andrews was wanted by police for questioning in relation to a murder inquiry. When the police found Andrews he shot himself dead after fatally shooting his female companion. Andrews was only 33, as stated in The Man Who was Erdnase.
Wilbur Edgerton Sanders

Some argue that Erdnase was probably a well educated, locally prominent individual, hiding behind an alias to protect his social standing. The most prominent individual mentioned in this regard is a mining engineer named Wilbur Edgerton Sanders, proposed by magician and private detective David Alexander. (Note that "S. W. Erdnase" is an anagram of "W. E. Sanders".)[1] Genii Magazine devoted a large portion of its September 2011 issue to an exploration of this theory.
E. S. Andrews

Todd Karr has identified a Midwestern-based con artist and business swindler named E. S. Andrews who was active around the turn of the century and whose biography and range of known locations seems to fit Erdnase's.[2]
L'Homme Masque

Juan Tamariz has advanced the theory that Erdnase was written by the Peruvian magician named "L'Homme Masque" (The Masked Man), who lived in Europe.

Juan Tamariz has the hypothesis that Erdnase was written by the 19th century Peruvian magician "L'Homme Masque" (The Masked Man), who lived in Europe and is considered one of the greatest magicians in history, even Dai Vernon himself considers him among the three greatest. During the 9th Congress of the Latin American Federation of Magic Societies (FLASOMA 2009) held in Peru, he explained the reasons and grounds for which the author of Erdnase has to be L'Homme Masque. During the explanation of this theory Gaetan Bloom was present, supporting this hypothesis.