On August 10th 1969, a "concerned citizen" addressed a communication to Sergeant John Lynch of the Vallejo Police Department and supplied the code key to the 408 cipher, stating "Dear Sergeant Lynch. I hope the enclosed "key" will prove to be beneficial to you in connection with the cipher letter writer. Working puzzles criptograms and word puzzles is one of my pleasures. Please forgive the absence of my signature or name as I do not wish to have my name in the papers and it could be mentiond by a slip of the tongue. With best wishes. concerned citizen". The author of this communication (who many believe to be the Zodiac Killer) also gave us a variant spelling (albeit incorrect) of "cryptogram", by using "criptogram". The author also expressed an interest in "word puzzles" on August 10th 1969. So was the Zodiac Killer's inspiration for the July 31st 1969 letters derived from the Sunday newspaper puzzle page?
Thanks to Cragle for the information used in this article.