Walter Henry Breen Jr. (September 5, 1928 – April 27, 1993) was an American numismatist, writer, and convicted child sex offender.

[2] At the time they met, both of Walter's parents were married to other people and living next door to each other in Parkersburg, West Virginia.

After being declared unfit for service by the United States Army Air Forces in April 1946, Breen was accepted that October with a recorded IQ of 144;[4] following a severe beating,[5] he was honorably discharged that December.

During his recovery, he read voluminously about rare coins and initiated correspondence with various members of the numismatics community, renewing his involvement in a hobby in which he had been actively engaged a few years earlier.

[5] Alternatively, Breen claimed that a severe head injury suffered in a World War II plane crash led to the development of his photographic memory.

After graduating Phi Beta Kappa, he took a position as an auction cataloger for the New Netherland Coin Company while concurrently enrolled in pre-med courses at Columbia University, where he became a protege of the controversial psychologist and numismatist William Herbert Sheldon.

[5] Breen eventually enrolled in the sociology graduate program at the University of California, Berkeley, where he claimed to have researched "the Beat Generation groups on both coasts but also some of the very earliest hippies, finding out incidentally that some ideas that the bunch of us had developed in science fiction fandom had gotten into the hippie subculture and were being paraded around as their own inventions.

Breen was initially convicted of child molestation or lewd behavior in Atlantic City in 1954, resulting in a probationary sentence.

[6][14] In 1963–1964, allegations of further sex crimes caused within science fiction fandom a controversy known as "Breendoggle"; Breen was banned from attending Pacificon II and briefly blackballed from the subculture's main amateur press association.

[14] Nevertheless, prominent fans of the era (such as John Boardman and Ted White) dismissed the allegations as hearsay and "character assassination," and the scandal blew over.

[18] In 2014, Breen's daughter Moira Greyland revealed that she was one of the people who reported her father for child molestation.

[19] In addition to his employment with First Coinvestors, Inc., where he was an officer for many years, Breen was an active member of the science fiction fan community for much of his life.

[6] A user of marijuana and LSD, Breen believed in reincarnation, often recounting putative past lives in Atlantis, ancient Greece, and other mythological and historical epochs.