S. W. Erdnase was most likely a way for the author to conceal his real identity so he wouldn't be arrested, since Federal laws at the time prohibited the publication and distribution of "obscene" material. In the late 19th and early 20th century, many judges considered books on gambling methods obscene (see Comstock laws). S. W. Erdnase spelled backwards is "E. S. Andrews" leading many investigators to search for people named Andrews as possible candidates.
Martin Gardner has proposed that a small-time con man named Milton Franklin Andrews was the author. Another proponent who researched this theory was Barton Whaley, in his book The Man Who Was Erdnase, which contains eyewitness interviews from the 1940s. 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.
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.
There has been newer evidence since the year 2000 that puts to rest the assumption that Milton Franklin Andrews was Erdnase. It is obvious that Andrews was a card cheat but that is as far as his connection goes. Other historians have also found other men that could have indeed been S.W. Erdnase.
Some argue that Erdnase was probably a well-educated, locally prominent individual, hiding behind an alias to protect his social standing. The late David Alexander, a magician and private detective, did quite a bit of work to find a better and more possible candidate than Milton Franklin Andrews, and he proposed that Erdnase was a prominent mining engineer named Wilbur Edgerton Sanders. (Note that "S. W. Erdnase" is an anagram of "W. E. Sanders".)
Since Alexander's death, others have researched Wilbur Edgerton Sanders. Genii Magazine devoted a large portion of its September 2011 issue to an exploration of Alexander's theory, providing substantial circumstantial evidence that links Sanders to Erdnase.
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. Also, E.S. Andrews spelled backwards is S.W. Erdnase.
Juan Tamariz has advanced the theory that Erdnase was written by the Peruvian magician named "L'Homme Masqué" (The Masked Man), who lived in Europe.Juan Tamariz tiene la hipotesis que el Erdnase fue escrito por el mago peruano del siglo XIX L'Homme Masqué que vivió en Europa y es considerado uno de las más grandes magos de toda la historia, hasta el propio Dai Vernon lo considera entre los tres más grandes. Durante el IX Congreso Latinoamericano de Magia FLASOMA 2009 realizado en Perú, explicó las razones y el fundamento por el cual el autor del Erdnase fue L'Homme Masqu&eqacute;. Durante la explicación de esta teoria estuvo presente Gaetan Bloom respaldando esta hipotesis.
Juan Tamariz has the hypothesis that Erdnase was written by the 19th century Peruvian magician "L'Homme Masqué" (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 Masqu&eqacute;. During the explanation of this theory Gaetan Bloom was present, supporting this hypothesis.
Many other people have also been proposed, including James Andrews, James DeWitt Andrews, Robert Frederick Foster and Herbert Lee Andrews, which have been discussed and debated on the Erdnase topic on the Genii Forum since 2003
A film based on the life of the mysterious author, adapted by German director Hans-Joachim Brucherseifer, is currently in production. The magicians Yann Yuro (S.W. Erdnase) and Alfonso Rituerto (himself) play the lead roles. It is scheduled to be released in November, 2020.