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The “Celebrity Cipher” postcard has been mailed from Oakland, California to Vallejo Times Herald in September 1990.
The front side of the card is split into two halves through a thick vertical line. The card is titled “Sandy Beaches – California” at its footer on the left and carries a stamp with an image of American Modernist poet Marianne Moore at its top right.
The cipher has been named “CELEBRITY CYPHER” [sic] by its author and addressed to “VALLEJO TIMES HEROLD” [sic]. Cipher name and recipient address were written in capital plain text letters.
Based on a handwritten note below, the card’s “POSTMARK IS OAKLAND 9-25-1990”. A second handwritten note suggests that the card refers to “LAKE BERRYESSA ANNIVERSARY OF 9-21-1969”. A third handwritten note states “REVERSE OF CARD DRIFTWOOD ON OCEAN BEACH”.
The code symbols shown in the card closely resemble symbols used in the Zodiac Killer’s infamous 340 character cipher (Z 340).
The Celebrity Cipher code comprises 31 visible symbols with 63 visible occurences. The most frequent symbols  , ,  occur 6, 5, 4 times. Six symbols occur 3 times, 8 symbols 2 times, and 14 symbols only 1 time each. There is an apparent misalignment in line heights, comparing the left and right cipher parts, suggesting that the cipher starts on the left and continues on the right. Three symbols or characters in the third line on the cipher’s left resemble the plain text letters “FBI”. The first 2 cipher lines on the left and the last two cipher lines on the right part of the card appear to be identical.
There are clusters of coherent cipher symbols of different length, with spaces between the clusters, which suggested possible word lengths. Line 4 of the cipher shows a sign resembling a comma. There is a cipher symbol very close to the stamp that resembles the symbol in rather italic writing style, or represents an additional cipher symbol similar to a slash sign, or the visible part of a symbol with its remainder hidden behind the stamp. Due to the very close proximity of this symbol to the stamp, there is a possibility that 1-2 additional cipher symbols could be hidden behind.
Similar to the Z 408 and Z 148 ciphers, the Z 63 is a simple substitution cipher that has been enhanced to homophonic substitution by adding extra symbols to single alphabetic letters to disguise letter frequencies. For instance, seven different symbols have been allocated to the letter “E”. Furthermore, through the cipher author’s choice of words, the letter “P” became a frequent letter. In normal English language, this letter occurs with a frequency of about 2%, while it nearly has a 10% frequency in the Z 63 cipher. Consequently, any attempt using common letter frequencies to crack the cipher were futile.
What additionally made the cipher difficult to crack was its short length of just 63 characters; even only 50 characters if the repeating headline is excluded. Futhermore, the random spaces and non-spaces between words as well as variations in line breaks increased the level of difficulty. Similar goes for the apparent “FBI” letters at position F3-H3 that were just symbols and not plain text apparently. An additional challenge posed our unfamiliarity with the English word “DIRGE” that we could not easily identify as such.
While we believe that our cipher solution is rock solid, there are still possible variations that, at least at this point, are impossible for us to eliminate.
For instance, we are not certain if the  at K6 is an additional symbol. It could represent the symbol that is already available at other locations of the cipher or could stand for another symbol that is or is not in the cipher at other lcoations. For instance, it could stand for the letter “W”.
Furthermore, we are not sure if the stamp on the card doesn’t hide additional symbols. What looks like a slash sign might be another sign partially hidden, and there would be space for two additional signs behind the stamp. However, this is speculation, and for pragmatic reasons we only worked with the obvious.
Finally yet importantly, the symbol  at B8 occurs only once in the entire cipher. If A8-B8 represents an English word, then the only possible interpretation is that it represents the letter “X”. Another possibility would be that it stands for the letter “N” to form the French word “EN”, considering that “DIRGE” is also a French and not only an English word. Other possibilities that we would see are that the A8-B8 cipher positions represent initials or an acronym. In such case, the symbol could assume nearly every letter of the alphabet.
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