I was lucky enough to get my hands on the actual San Francisco Chronicle newspaper, in its entirety. All newspapers from 10/12/70-10/17/70.

Of course this is the edition which published the October 5th, 1970 postcard.

It really got me to confirm my personal belief this was NOT from Zodiac. Paul Avery had been writing Zodiac articles for a year prior to this. (see link below). It is only after this card (which was not addressed to Paul) got published that the next one (the Halloween card) came addressed to Paul. I believe Paul Avery gave THIS person attention and therefore, this person became infatuated with Paul.

PAUL AVERY ZODIAC ARTICLES: viewtopic.php?f=85&t=1385

Let’s not forget…Zodiac had already claimed "13"…months before this card.

Thanks for posting it Tahoe

So then you must not believe that the Halloween Card mailed on Oct 27th 1970 when he gave a clue to the number 14 is real either ? The list seems to be dwindling, curious as to which ones you believe are real ? I don’t mean to sound sarcastic , I am really curious .

I have that page in my Z collection , the article next to it caught my eye yrs ago , because of the Pup fish . There was a victim Dana Lull in Las Vegas ,who was possibly taken by Harvey Hines’s suspect Larry Kane. When Kane was pulled over in that desert, he had a sign on the back of his small car that read : Save The Pup fish. I had searched everywhere to find any information on Pup fish including the SF Steinhart Aquarium , they had no idea about those fish. It wasn’t until I went through my collection of Chronical newspapers that I found the information. Just one of those strange coincidences that the information was next to a Zodiac communication.

Thanks for posting it , for some reason I thought it had been posted long ago.

I have not believed the HC card was sent by Zodiac for quite some time.

10/5/70
The Adams card (You’re next) – 10/17/70
HC 10/27/70
The Pines Card 3/71

The same person, just not Zodiac, in my opinion. viewtopic.php?f=70&t=162 & here: viewtopic.php?f=72&t=59&start=70

This article has been shared, I just wanted to show how it looked in the paper–on the cover and full page.

–Just a side note in regards to the SF Chronicle. I found it interesting all of Graysmith’s political cartoons were just above the letters to the Editor. (It means nothing…just caught my eye).

Interesting…I never new the cross was drawn with blood.

Apparently, that was a misconception. It wasn’t blood.

There is obviously a concealed, shifted-alphabet cipher in this ‘Thirteen’ postcard, too. The solution is not entirely trivial, but a professional cryptanalyst or censor should have at least called the presence of this specific type of cipher. Such a cipher is detected by the awkward choice of words, their unnatural arrangement, alignment with controls (numbers and enumerable holes), irrelevant text (“Some of Them Fought”, “It Was Horrible”), etc. I found interesting discussions of the postcard on the web and on this board, but nothing about the cipher – was the card not analyzed by a cryptanalysis lab? Perhaps the card was prematurely dismissed as non-authentic, or suffered from the general skepticism about any real content in Zodiac’s puzzles.

First, note that unlike all earlier communications sent by Zodiac, here he used “S.F.” instead of “San Fran” to indicate the use of initials, as customary in this type of classic cipher (see any introductory book). The date and its unique format are very unusual for Zodiac, so clearly part of the cipher. The holes are arranged in a deliberate pattern to indicate the alphabet shift s of each part of the message. The number 13 split by a comma into “1,3” is clearly a control, indicating here an s=3 transition in resemblance of the Sierra postcard. The Zodiac symbol and cross suggest the use of quadrants, i.e., the message is split into four parts. The upside-down text indicates that the postcard should be rotated for top, side, and bottom reading. Etc.

This cipher shows striking similarities to those concealed in the Sierra postcard (card rotation, s change disguised as a body count, message reversal, etc.) and the Eureka card (alphabet direction change, double use of an alphabet letter, etc.). The three communications – Thirteen, Sierra, and Eureka – can be attributed to the same author, at a very high likelihood, on this basis alone. Thirteen is more difficult and disorganized than the two other cards, and therefore more challenging to solve and prove unique. One can see how the author improved from Thirteen to Sierra to Eureka, gradually giving up on disorganized elements, letter swaps, etc.

One difficulty in Thirteen is that, unlike Sierra and Eureka, there is no fixed key. Without such a key, the Thirteen message is not as singularly unambiguous as Sierra and Eureka. Preparing this type of cipher without a key requires frequent changes in s and/or alphabet inversions. Thirteen includes coherent sentences, unlike the other cards, suggesting that the cipher uses only the first initial of the sentence rather than all word initials. For instance, “pass LAKE TAHOE areas” (in Sierra) is an unnatural sentence indicating that all initials ‘PLTA’ are part of the cipher. In contrast, “Some of Them Fought” (in Thirteen) is coherent, so only the ‘S’ is likely used.

The figure below shows the postcard with red, cyan/blue, and green annotations corresponding to the three words in the cipher. Initials are identified as ordered cipher letters by colored numerals. The alphabet direction is indicated by heavy arrows, message reversal by dot arrows, and letter reading direction by normal arrows (see legend); alphabet shifts are designated by mapping ‘a’ and the corresponding s value. While the choice of initials, reading order, and s values are not entirely unique, they are reasonably well justified by the postcard structure and its control symbols. Notably, the ambiguity is quite restricted, and I could not find any other non-gibberish solution; you are welcome to try.

The cross splits the 13 holes such that the bottom part aligns with six holes (so |s|=6 for the green word), and the middle part aligns with the remaining seven holes (so |s|=7 for cyan letters). The top three lines were carefully aligned with three holes (so |s|=3 for the red word). The “1,3” control changes the shift within the cyan/blue word (from s=7 for cyan to s=3 for blue). These choices, consistent with Zodiac puzzles, are neither arbitrary nor entirely unique. The initials are ordered naturally and not forced, except the red “R” and “H” on the bottom left, which, as shown below, are not essential for the message.

This cipher interpretation is not particularly elegant, but that was inevitable given the messy structure of the card (Zodiac did improve in later ciphers). However, the presence of the cipher is unequivocal, and a non-gibberish, consistent alternative to my solution is highly unlikely, even with the two uncontrolled binary degrees of freedom (alphabet inversion and word reversal). Namely, I challenge anyone to find a meaningful alternative without arbitrary changes to the initials or their order, and with no more than three s changes (reasonably justified by controls).

The red word, obtained from “RMHOODY” with s=-3 and a regular alphabet, is “ojellav”; word reversal gives “vallejo”. Without the red “R” and “H” on the bottom left, “MOODY” would yield “vallj”, which is not as good but still understandable. The cyan/blue word, obtained from “TFSI” with s=7 (cyan) or s=3 (blue) and a regular alphabet, is “mill”. The green word, obtained from “ZNPST” with s=6 and an inverted alphabet, is “htron”; word reversal gives “north”. Combined, we have “Vallejo Mill North”. But we already knew that, and it is not surprising to see this message sent a few weeks before the Halloween card. And the card is definitely the Zodiac speaking.

Posted by: @urik

There is obviously a concealed, shifted-alphabet cipher in this ‘Thirteen’ postcard, too. The solution is not entirely trivial, but a professional cryptanalyst or censor should have at least called the presence of this specific type of cipher. Such a cipher is detected by the awkward choice of words, their unnatural arrangement, alignment with controls (numbers and enumerable holes), irrelevant text (“Some of Them Fought”, “It Was Horrible”), etc. I found interesting discussions of the postcard on the web and on this board, but nothing about the cipher – was the card not analyzed by a cryptanalysis lab? Perhaps the card was prematurely dismissed as non-authentic, or suffered from the general skepticism about any real content in Zodiac’s puzzles.

First, note that unlike all earlier communications sent by Zodiac, here he used “S.F.” instead of “San Fran” to indicate the use of initials, as customary in this type of classic cipher (see any introductory book). The date and its unique format are very unusual for Zodiac, so clearly part of the cipher. The holes are arranged in a deliberate pattern to indicate the alphabet shift s of each part of the message. The number 13 split by a comma into “1,3” is clearly a control, indicating here an s=3 transition in resemblance of the Sierra postcard. The Zodiac symbol and cross suggest the use of quadrants, i.e., the message is split into four parts. The upside-down text indicates that the postcard should be rotated for top, side, and bottom reading. Etc.

This cipher shows striking similarities to those concealed in the Sierra postcard (card rotation, s change disguised as a body count, message reversal, etc.) and the Eureka card (alphabet direction change, double use of an alphabet letter, etc.). The three communications – Thirteen, Sierra, and Eureka – can be attributed to the same author, at a very high likelihood, on this basis alone. Thirteen is more difficult and disorganized than the two other cards, and therefore more challenging to solve and prove unique. One can see how the author improved from Thirteen to Sierra to Eureka, gradually giving up on disorganized elements, letter swaps, etc.

One difficulty in Thirteen is that, unlike Sierra and Eureka, there is no fixed key. Without such a key, the Thirteen message is not as singularly unambiguous as Sierra and Eureka. Preparing this type of cipher without a key requires frequent changes in s and/or alphabet inversions. Thirteen includes coherent sentences, unlike the other cards, suggesting that the cipher uses only the first initial of the sentence rather than all word initials. For instance, “pass LAKE TAHOE areas” (in Sierra) is an unnatural sentence indicating that all initials ‘PLTA’ are part of the cipher. In contrast, “Some of Them Fought” (in Thirteen) is coherent, so only the ‘S’ is likely used.

The figure below shows the postcard with red, cyan/blue, and green annotations corresponding to the three words in the cipher. Initials are identified as ordered cipher letters by colored numerals. The alphabet direction is indicated by heavy arrows, message reversal by dot arrows, and letter reading direction by normal arrows (see legend); alphabet shifts are designated by mapping ‘a’ and the corresponding s value. While the choice of initials, reading order, and s values are not entirely unique, they are reasonably well justified by the postcard structure and its control symbols. Notably, the ambiguity is quite restricted, and I could not find any other non-gibberish solution; you are welcome to try.

The cross splits the 13 holes such that the bottom part aligns with six holes (so |s|=6 for the green word), and the middle part aligns with the remaining seven holes (so |s|=7 for cyan letters). The top three lines were carefully aligned with three holes (so |s|=3 for the red word). The “1,3” control changes the shift within the cyan/blue word (from s=7 for cyan to s=3 for blue). These choices, consistent with Zodiac puzzles, are neither arbitrary nor entirely unique. The initials are ordered naturally and not forced, except the red “R” and “H” on the bottom left, which, as shown below, are not essential for the message.

This cipher interpretation is not particularly elegant, but that was inevitable given the messy structure of the card (Zodiac did improve in later ciphers). However, the presence of the cipher is unequivocal, and a non-gibberish, consistent alternative to my solution is highly unlikely, even with the two uncontrolled binary degrees of freedom (alphabet inversion and word reversal). Namely, I challenge anyone to find a meaningful alternative without arbitrary changes to the initials or their order, and with no more than three s changes (reasonably justified by controls).

The red word, obtained from “RMHOODY” with s=-3 and a regular alphabet, is “ojellav”; word reversal gives “vallejo”. Without the red “R” and “H” on the bottom left, “MOODY” would yield “vallj”, which is not as good but still understandable. The cyan/blue word, obtained from “TFSI” with s=7 (cyan) or s=3 (blue) and a regular alphabet, is “mill”. The green word, obtained from “ZNPST” with s=6 and an inverted alphabet, is “htron”; word reversal gives “north”. Combined, we have “Vallejo Mill North”. But we already knew that, and it is not surprising to see this message sent a few weeks before the Halloween card. And the card is definitely the Zodiac speaking.

It’s weird how some people look at something like this letter and see a letter, to others so many messages and meanings pop out. The human mind is an odd thing 

Posted by: @morf13

It’s weird how some people look at something like this letter and see a letter, to others so many messages and meanings pop out. The human mind is an odd thing 

Yes, different people see different things. Those who haven’t experienced concealed alphabet ciphers may see a strange postcard here, just as those who don’t know about homophonic ciphers may see Z340 as a piece of art. Similarly, few might read your comment as marveling at how Zodiac’s message can be carefully disentangled from his messy puzzle decades after its creation, while most people would understand what you meant.

But seriously, does anyone look at this bizarre card and just, as you say, see a letter? I think most people realize something is strange and non-innocent in this card, and many sense that it contains some puzzle. If anything, most would dismiss it not as a letter but as a meaningless hoax or an eccentric/artistic creation. But again, not those of us who studied cryptography and appreciate these classical alphabet ciphers, concealed effectively over centuries and up to 1960s (at least) espionage. People were trained to detect subtle indications for such concealed ciphers, and would instantly identify or at least classify the cipher in this card if given a chance.

The Sierra and Eureka cards are just better, more mature versions of this card. Do their strange elements (scattered words and numbers, keys, etc.) also look innocent to you? A well-trained cryptanalyst would consider the three cards to be trivial demonstrations of concealed shifted-alphabet ciphers and how they can be improved. Unlike real-world ciphers, Zodiac’s messages were not even meant to fully evade detection, reach a third party with a private key, or remain unsolved forever. Note that the challenge of a concealed cipher is detection and classification; solving it is easy and only took me a few hours yesterday.