As is now well known, the skeleton figure added to the inside of the card was carefully cut from another Halloween card and added as an insert within this one for whatever specific reason. An original of the card the skeleton came from has been sourced (see here, posted on Reddit), showing us clearly that the eyes of the skeleton are an addition by The Zodiac and that, in its sourced form, it had merely the rectangular opening of precisely the shape that we see in his modified version through which another (cuter) pair of eyes originally peered.

Yet, the eyes remained important (undoubtedly), and so the Zodiac added his own in white on a reddish background.

But if we now focus on these eyes, together with the raised position of the arms and dropped hands, we basically have the majority of the symbol that appears below it. And I, personally, find it hard imagine that the archetype for this symbol was anything other than just this very pose by his added skeleton.

Thus, again to me, I feel I can, with confidence, propose that this figure (symbol), together with its several additions, is not something that has any existence or relevance beyond what it conveys in the context of just this card—essentially, that it is not an insignia of any kind, or a brand, or any such thing having external meaning.

And, furthermore, it now seems pertinent that, for some purpose that we are attempting to decipher, the primary annotations effectively reduce to the lower pair of dots and just the single line.

as from the viewpoint of Mount Diablo.

I can't speak for how 'evident' this idea might appear to others, though, and I acknowledge that, over time, I have probably been seeing the figure in this way to the extent of having ultimately formed an unhelpful bias.

Yes, these are two of the more talked-about interpretations of what may be the basis for the 'Halloween symbol', if we call it that. I can even recall being on the message boards around the time these, and other, ideas were originally floated and discussed.

For me, though, where both of these fall short in my judgement is that neither interpretation leads us to any understanding of what it is that the addition of this symbol to the card is intended to convey to us. What is it saying?

If the identifiable cattle brand from a Colorado rancher, then ... what? What has cattle ranching got to do with anything? Where's the missing bar that is part of the brand at the bottom, as in appears in Red Ryder? What does the 4-dot annotation say to us, when added to this incomplete cattle brand? For me, then, this line of thinking, although initially mildly compelling, just doesn't take us anywhere.

The same goes, pretty much, for the double peak of Mount Diablo. What is so important about how it appears from this specific vantage point in Concord? If Mount Diablo has any relevance to us at all in interpreting the symbol on the card, it has to be in connection with his use of this peak as the coordinate origin in locating his bomb on the Phillips 66. But what further information does this figure, interpreted in this way, add to that particular conundrum? Diablo is the starting point of our search for the bomb, not the end point? What purpose does any given view of our origin, here, add to the solution of the problem before us?

So that's why, having likewise seen in it the line-image of a two-peaked hill range, I have to suppose that it has specific relevance to the end point of our radian, the location where the bomb is set; the place where we would have to go to "dig it up." And when we start out with this in our minds, then I personally feel that it becomes pertinent now to ask how specifically is it that the annotations—the dots and the lines—are giving us the extra detail that we sorely need, when before we could extract no meaning from them at all.

https://mdf-alias-mostrodifirenze.blogspot.com/2024/01/il-simbolo-e-la-mappa.html

1 - Zodiac researcher Morf13 explained here that Fred Harman III, Red Ryder’s inventor son, was the real owner of the cattle brand (here’s the same symbol in the Colorado Brand Book 1948, page 508, n. 29 – source);

https://ostellovolante.com/2020/08/05/zodiac-halloween-riddle-and-italian-cuckoos-game/

We are taking it as given to us that we are viewing this hill pair from the top of Mount Diablo, thus looking somewhat down on it, and that to our view at this location the orientation of the pair towards our right is to the North. And this, of course, can only be the case if, in looking in the correct direction we, ourselves, are facing broadly West.

This, then, is the direction we should be looking in.