…i.e. was he a member of broadly the same group of Odd Fellows that used the Action Line Cryptogram to acrostically encrypt their initiation ceremonies?
In South Australia, Odd Fellows founded their first Lodge in Adelaide in late 1840 (according to this 1843 page from their journal), at just about the same time as a Lodge was formed in Sydney: and even today, Odd Fellows in SA are apparently still going strong.
So… looking again at the Tamam Shud text, it parallels the Action Line Cryptogram: that is, it gives cryptologists a very strong impression of having been constructed as an acrostic English ciphertext, because its letter frequency distribution closely follows the same frequency distribution pattern found in English texts.
All the same, pure acrostic cryptograms are relatively rare in the wild, because they are more mnemonic than cryptologic: they are there to remind the reader of something they already know rather than to communicate something unexpected to someone else. The more personal the message, the more unknowable its contents: and that’s they way it is, I guess.
So perhaps in this instance Marshall McLuhan is right, and the medium (an Odd Fellows-style acrostic cryptogram) is the message. If so, the most we are likely to infer from this is that it was written by someone who was (or had been) a member of an Odd Fellows Lodge, very probably in Adelaide itself. The Somerton Man may well have been down on his uppers (albeit very shiny uppers), but I expect those same shoes had likely been inside an Adelaide Lodge at some stage.
Now, Pete Bowes will likely take this as a cue for explaining why (in his belief) the contents of the suitcase were laid out in such a ceremonial way: and why the name link to recently-deceased Adelaide Freemason Tom Kean was never explored by the police. But… one thing at a time, Petey-boy, one thing at a time… 🙂