We have two June communications separated by two years, both extremely brief in nature and connected to baseball, with both signed by the pseudonym "Zodiac" and mailed on the Thursday before the Saturday in question. Each letter was focused on the Saturday, The Oakland A's tickets were chosen for Saturday, June 20th 1970, encouraging the recipients to leave their house on 1423 Roleen Drive and attend the baseball game, whereas the letter to Edward J. Salmina on June 29th 1972 was encouraging him not to leave his house on the next ten Saturdays (and probably threatening him not to attend the baseball). The second author in 1972, if different to the one in 1970, could never have imitated the original threat without inside knowledge.
The 1972 Novato letter threatening to kill Edward J. Salmina contained a series of symbols under the heading "message" (believed to be a short code). This is extremely interesting, because the next letter we know of (claimed to be from Zodiac) also contained a short code, while claiming he would kill on a specific date. The author of the Albany letter, mailed to the Albany Times Union newspaper in New York on August 1st 1973 and targeting the Albany Medical Center, promised to "kill her on August 10th at 5:00pm". The author of this letter gave a specific time he would murder, just like the author of the Novato letter who stated "If you leave your house past 3:13:47 on the next ten Saturdays, you will be killed". This was unique to both these letters. Although the Albany message was issued on a Wednesday for a week Friday, it was again issued with time being the central focus. The two 1970 Oakland A's tickets bore a time and date, the 1972 Novato letter bore a time and ten dates, as did the Albany letter in 1973. All three letters were aimed at a specific individual - Gerald Tagert, Edward J.Salmina and Connie Henly (from the decoded portion).