Page 2 of the 7/31/1969 letter to the SF Examiner, one of three received on that date that section 2/3 of the 408 cipher.

 

 

Page 2 of the 7/31/1969 letter to the SF Chronicle, one of three received on that date that contained section 3/3 of the 408 cipher.

 

 

z340, included with the “Dripping Pen” card received 11/8/1969. Image credit to David Oranchak.

 

August 1969 letter to SF Examiner. Zodiac “Debut” letter

 

pages from letters dated 10/13/1969 (the Stine letter, mailed to SF Chronicle) and 12/20/1969 (The Belli Letter mailed to Melvin Belli's home address)

 

page 1 from letter to SF Chronicle dated 4/20/1970.

 

letter to SF Chronicle dated 6/26/1970, sent with Phillips 66 Map and cipher included.

 

DISCUSSION

 

My conservative, fully jaded appraisal of this observation is that it is most likely not that useful, especially given the possibility that watermarks on certain letters are simply not resolvable with the scans publicly available online.  Even if we could be 100% sure which letters have watermarks or don't, the most it really demonstrates is that some letters were probably written from a common ream, and therefore the watermarks simply reinforce the notion that, at the very least, these letters are from a single author, which is already the official status of the letters sampled above.

Having said that, if this is genuine data and multiple paper stocks were used for different Zodiac communications, then I have some interesting observations to share (interesting to me) regarding their distribution over time and contents that are worthy of note; fertile ground for some classic speculation and, hopefully, discussion.

 

First, not every cipher is on or accompanies a letter written on paper with a SAKS watermark. As far as I can tell, the letter with the Mount Diablo code (6/26/1970) does not have a watermark.  That scan is of particularly high quality, better than any other I have looked at in the hunt for these watermarks.  Additionally, the “My name is” cipher (4/20/1970) does not appear to be on SAKS paper, although the available scan image is particularly low resolution.

 

However, these two ciphers were also received in a relatively short space of time, within 2 months of eachother.  This is roughly equivalent to the time between the receipt of z408 and z340. Notably, the time between the receipt of z340 and the “My name is” cipher is nearly 5 months.  If we treat the z408/z340 letters as a pair, and do the same thing for the "My Name Is" and Mount Diablo Map code, then that 5 month respite constitutes more than double the latency between ciphers of the same group.  This is hardly an earth shattering insight, but it seems that Zodiac might have abandoned this SAKS branded paper stock sometime between November 1969 and April 1970, or possibly before the Belli letter in late December, 1969 whether this was an intentional or incidental choice.

 

Second, there are two letters that contain schematic type diagrams of electrically powered, photosensitive bombs. The first, received 11/9/1969, one day after the “Dripping Pen” card and z340 cipher, includes at least one page with a SAKS FIFTH AVENUE watermark. The second, the “My Name Is” letter does not appear to have this watermark.  Again, this might be simply a result of Zodiac generally abandoning this paper stock in favor of another, and that change need not be any more complicated than he exhausted one ream of SAKS paper and moved on to another that simply didn't have this characteristic.

 

The issue is that there are letters received prior to November 9, 1969 that, as illustrated above, might not have this watermark and, therefore, would have been written on different paper stock from a different ream.  If they do have the watermark, I cannot see it.  If I can't see it, there's a possibility that it's not there.  While I can think of several trivial reasons for that to happen, one intriguing possibility is that watermark and non-watermark letters were written in different locations with different supplies on hand.

 

The two main examples of these pre-November non-watermark letters would be the Zodiac “debut” letter from August 1969 and the “Stine” letter from October,1969.  What stands out to me about these letters is that neither contain schematic, technical information or are accompanied by ciphers.  Conversely, while I can't opine on the July 31 letter to the Vallejo Times Herald for reasons I have enumerated above, every letter prior to December 20, 1969 is either accompanied by a cipher or a technical illustration.  This could potentially suggest that these letters might have been written in the presence of books, possibly in a library, an office or workshop with technical manuals or textbooks, perhaps as simple as a study with a bookshelf containing either legitimate resources on electrical engineering, basic cryptography, and chemistry, or non-professional titles, perhaps underground books like the Anarchist's Cookbook.  These resources would, in turn, be on hand for the author as he tried to generate functional ciphers and credible bombs.  There are a number of location types that could supply such resources, including something as simple as a study in the author's house, as long as there is sufficient reason for the office supplies used by Zodiac in either case to be segregated.  Non-watermark letters, in contrast, would not leave the author in need of references and could be written anywhere, whether that's substantially far away or as close as a kitchen table of living room.

What matters though is whether it is a place other than his residence because, unless he brought his own paper from home, then it would mean Zodiac was writing multiple letters at a single place at different times and the paper was sourced from that location.  That, again, could be a library, and office, some sort of workshop; anywhere.  The exciting thought is that it might have been A) a public place where people knew him, and/or B) a place with a negotiated contract with a supplier that might have delivered the same paper stock over an arbitrary period of time and leaving behind a record. 

 

I think that's about as far off the reservation as I'm prepared to take this idea at the moment.

 

To be clear, assuming this distinction between watermark letters and non-watermark letters even exists, it in no way necessarily follows that, therefore, they must have been written in different places.  50 years from Zodiac's spree, with each passing year we're grasping at successively smaller straws, and that's ultimately the spirit of this lead.  If nothing else, at least it's interesting to think about.