In the letter provided in the Oakland Daily Evening Tribune, the author uses the pseudonym NEMO. The proposed theory is the NEMO is Charles Howard Shinn, who was an avid writer and authored many books during his time. Additionally, NEMO has detailed knowledge about the Shinn Nursery and its history, information that an outsider would not be privvy to. The book Twenty Thousand Leagues Under the Sea was published 1872, meaning that Shinn would have to have been at least 20 years old when he first read the novel. Furthermore, the Shinns had an extensive library with one of the books being Twenty Thousand Leagues Under the Sea. The letter itself was published in 1879, five years after the publication of the novel, meaning that Mr. Shinn would have been around 25 years old when he wrote it. 

Other potential authors of the letter may include a member of the Oakland Daily Evening Tribune who either worked there or had person connections to the newspaper. The article also details the lives on many other people living in the area, meaning that is possible any one of the people mentioned may be our elusive Captain NEMO.