Secret Agent X-9 was a comic strip begun by writer Dashiell Hammett (The Maltese Falcon) and artist Alex Raymond (Flash Gordon). Syndicated by King Features, it ran from January 22, 1934 until February 10, 1996.
X-9 was a nameless agent who worked for a nameless agency. X-9 used the name “Dexter” in the first story (“It’s not my name, but it’ll do.”) and kept using it or being called by it in later stories, but acquired the name “Phil Corrigan” in the 1940s and decades later the strip was renamed Secret Agent Corrigan. The nameless agency was also briefly the FBI when the FBI was in vogue, but when the FBI became less popular, references to it were dropped and the agency was nameless again. Hammett and Raymond eventually left the strip.