Just been looking over these initial letters again with the mindset that this is the most likely place that he may have made errors, thus giving us some un-intentional clues. Especially the Vallejo Times letter as, if as theorised this was the third out of the three to be written, then this could be the mostly likely to throw something up. A few things become apparent;-

1. Cipher / Cypher – In the two SF letters he uses the word Cipher. The Vallejo letter uses Cyipher with the I squeezed in between the Y and the P. It seems as an afterthought, almost as if he knew he had spelt it differently. Especially when you consider that he later spells it Cipher in the same letter.
2. To add weight to the order of sending, The Vallejo letter is the only one that states “The others have BEEN mailed”. So it can been assumed that this was the last. The SF Chronicle is the first (Pen slowly running out during the writing & the overall neatness of the letter) and the SF Examiner was the second. Also the Cipher itself is in Felt tip so one would think that this was produced first and then the letters.
3. He basically tells the SF Chronicle that they have 1 part of a 3 part cipher, whilst the other two papers are left in the dark as to whether they have the whole thing or a part. Only to be told in the next line that the two other parts have been mailed to alternate papers.
4. Cipher, San Francisco Chronicle, San Francisco Examiner, Vallejo Times. This in itself is interesting as it shows that from the outset the Chronicle was his Newspaper of choice.
5. The Vallejo letter “pick of stray people and couples”. The other two letters simply either “lone people or people who are alone”. So it does seem that his main motive was indeed couples and not just opportunism.
6. He uses the word “And” instead of the usually “+” when referring to the two attacks.
7. He uses a Capital “G” on the first line under 4th of July only on the Vallejo, thus showing that he was better versed in Grammar than he would like us to believe.
8. Only the “S F Chronicle” letter alludes “In this cipher is my identity”. Why did he not state this in the other two if this was his main selling point for the papers to print the cipher.
9. The Vallejo envelope contains 4 stamps whilst the other two have only 2. Add this to the “Been Mailed” comment. Does this mean that this was posted a lot latter in the day hence the need for more postage to ensure that it arrived on time. Or was it simply because it was being mailed out of the S.F. area.