These communications are extremely similar to a communication mailed from Berkeley, California on October 17th 1970, which also used cuttings to convey the message, was addressed to Dr. Edw. C. Adams, and threatened "Adams You Are Next Zodiac". Three weeks prior to the November 10th 1969 mailing (October 21st 1969), a note stating "You're Next - Z" was thrown from an automobile at an 8-year-old girl in Anderson Valley in Ukiah, California. A few months before the Edward C. Adams communication, somebody rang a woman, again in Ukiah, threatening "This is Zodiac - you're next". This phraseology would be used five times from people claiming to be Zodiac (or Zodiac) from October 21st 1969 to October 17th 1970.
San Bernardino was recently the focus of the Riverside Police Homicide Cold Case Unit, when they reported that in 2016 investigators received a communication from an individual in San Bernardino who claimed that he had authored the three Bates letters on April 30th 1967, stating he was a troubled teenager at the time he sent the trinity of malicious handwritten letters to the Riverside Police Department, Riverside Press-Enterprise newspaper and Joseph Bates. In 2020, four years after the admission in the 2016 communication, the Homicide Cold Case Unit and the FBI Los Angeles Investigative Genealogy Team submitted the stamp for additional DNA analysis and subsequent interviews were conducted. The individual linked to the DNA evidence on the (2016) stamp admitted to writing the (2016) letter and sending it to the Riverside Police Department. The Riverside Police Department further stated that "Additional information was developed regarding a separate set of letters sent to Northern California police agencies. The author claimed to be the "Zodiac Killer", but the author ultimately admitted to sending the letters to keep the investigation going". Montclair, San Bernardino is 19 miles west of Terracina Drive on the Riverside campus. The three Bates letters on April 30th 1967 were also composed using holed notebook paper, just like the November 10th 1969 communication mailed from San Bernardino.
"Edward C. Adams spent most of his life in the Bay Area where he attended the University of California Berkeley for his undergraduate work and Stanford University for his medical degree. His residency in psychiatry was received at the Menninger Clinic, Topeka, KS. During the Korean War he was an instructor in the Medical Field Service at Fort Sam Houston, San Antonio, TX. After retiring from an active practice in Psychiatry he devoted his energies to travel, fly fishing, the study of poetry and the enjoyment of his family and many friends. During the time spent at his Carmel home he volunteered as a docent at the Robinson Jeffers Foundation. He was a member of the San Francisco Psychoanalytic Society and an active supporter of many environmental groups". The November 10th 1969 communication was mailed to somebody in Clarinda, Iowa, located 121 miles (by crow) from where Edward C. Adams studied psychiatry at the Menninger Clinic in Topeka, Kansas.
Thanks to Cragle for sending me this document.