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" is E. S. Andrews backwards, making Andrews the most likely true identity of Erdnase.

Milton Andrews

Martin Gardner has proposed that a small-time con man named Milton Franklin Andrews was the author (S. W. Erdnase spelled backwards is E. S. Andrews, lending support to the theory that Andrews was the author's last name). 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 "W. E. Sanders" is an anagram for "S. W. Erdnase".)

E. S. Andrews

Todd Karr has identified a Midwestern-based con artist and business swindler named E. S. Andrews (S. W. Erdnase spelled backwards), who was active around the turn of the century and whose biography and range of known locations seems to fit Erdnase's.

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 tiene la hipotesis que el Erdnase fue escrito por el mago peruano del siglo XIX L'Homme Masque 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 Masque. Durante la explicación de esta teoria estuvo presente Gaetan Bloom respaldando esta hipotesis.

Juan Tamariz has the hypothesis that Erdnase was written by the Peruvian 19th century magician L'Homme Masque, who lived in Europe and is considered one of the greatest magician in history, even Dai Vernon himself counts him among the three greatest magicians. During the IX Latinamerican Congress of Magic FLASOMA 2009 held in Peru, he explained the reasons and the foundation due to which the author of Erdnase has to be L'Homme Masque. During the explanation of this theory Gaetan Bloom was present, supporting this hypothesis.