Character Analysis
Genghis Cohen is the most renowned philatelist (stamp expert) in Los Angeles. Someone has to be, right? Metzger hires him to inventory and appraise Inverarity's stamp collection. Cohen first contacts Oedipa because he has noticed some "irregularities" among Inverarity's stamps (4.66).
Oedipa goes to see him at his apartment/office, where she finds that he "had a touch of summer flu, his fly was half open and he was wearing a Barry Goldwater sweatshirt" (4.67). Oedipa can't help but feel motherly toward this misfit.
Cohen reveals a number of stamps to Oedipa that seem to have been forged by Tristero. He is the first one to explain to her that the Tristero symbol is a muted Thurn and Taxis post horn. He later reveals an article suggesting that Tristero came to the United States during the Civil War and the start of the postal reform movement, and he discovers an old forgery that reveals that W.A.S.T.E. stands for "We Await Silent Tristero's Empire."
At the end of the novel, Cohen tells Oedipa about a mysterious bidder who has emerged to bid on the Tristero forgeries at the auctioning off of Inverarity's Estate. Cohen immediately assumes the man has come from the Tristero and wants to erase evidence of the organization's existence. The novel ends with Oedipa and Cohen at the auction, awaiting the crying of lot 49.
Throughout the novel, Cohen does a bunch to fuel Oedipa's conspiracy theory about the Tristero. But at least he's much more detail and evidence-oriented than Emory Bortz, the San Narciso professor, and Cohen's involvement seems to lend the entire conspiracy some hint of respectability. Even when Oedipa begins to lose interest toward the end, she still listens to and relies on Cohen.
Cohen's name evokes the obvious pun on Genghis Khan, the founder of the Mongol Empire notorious for his brutality. As in many other instances in the novel, the purpose of the pun— aside from just being an oddball bit of wordplay—is totally unclear.