The "good citizen" letter was postmarked October 7th 1969 and mentioned 56 Beach Street, which is the old block numbering from the original planning maps, which comes out as 1654/1656 on the street numbering. The address at 1654/56 Beach St, San Francisco, California is a condominium home that measures 2,141 sq ft, and was built in 1938. Irrespective of the exact numbering, Beach Street is just 240 meters from the Presidio of San Francisco, where eyewitnesses saw a white male, about 40 years of age, weighing 170lbs, sporting a blond crewcut and wearing glasses, running into Julius Kahn playground shortly after the murder of Paul Stine on October 11th 1969. Of all the places in northern California or the Bay Area the author could select, the composer of the "good citizen" letter was not only referring to Zodiac's code letters, but managed to choose the location of Beach Street, bordering the Presidio in which the Zodiac Killer possibly escaped into just four days later. Possibly coincidence, but noteworthy nonetheless. The "good citizen" author may have been referring to Beach Street in San Francisco just a matter of days before the Zodiac Killer first struck in the big city, before mailing a letter on October 13th 1969, again detailing a destination in the form of a street name - this time "Washington St and Maple St".
The Zodiac Killer wanting a TV audience in San Francisco on October 22nd 1969 after his murder of Paul Stine in San Francisco eleven days earlier, can be argued. It is also possible that the Zodiac Killer may have rang into the Jim Dunbar Show "two or three weeks" earlier (between October 1st and October 8th), requesting a slot on the show to announce his intentions of bringing terror to the heart of San Francisco. A phone call placed to the Jim Dunbar Show in San Francisco on October 8th 1969 would coincide with the "good citizen" letter on October 7th 1969, also possibly involving a location in San Francisco - and both would predate the murder of Paul Stine in San Francisco by just a matter of days. A murder, in which the Zodiac Killer was spotted entering the Presidio grounds, which Beach Street borders. If we are to determine whether the "concerned citizen" card on August 10th 1969 was mailed by the Zodiac Killer, we have to factor in the letter on October 7th 1969 and the phone call to the Jim Dunbar Show around the same time - and the significance they may, or may not hold.