An independent scholar on the Book of Abraham, Paul Osborne, proposed in recent years that the printing plate for Facsimile 3 of the Book of Abraham was altered in such a way as to indicate that the figure originally had an Anubis-like snout.
Looking at the lead printing plate, we can see that something of a snout-like shape is indeed present. I think Osborne's argument may indeed indicate that something has happened.
His argument does face a couple hurdles, however.
To my understanding, Facsimile 3 was printed only once during Joseph Smith's lifetime. Since that printing, the plate has seen a number of alterations and has gone through a number of different hands.
The original 1842 Facsimile 3 in The Times And Seasons looks different than it looks in today's scriptures, and looks different than the printing plate. Some of these alterations may have been intended to smooth over the appearance, but may have had the effect of chopping off important details. I noticed this when exploring evidence of an extant Falcon on the Standard glyph at the top of the first column (a glyph which would be very unexpected, especially in such an intricate form, but which fits with a larger theory I've been working on).
So, the printing plate does not provide us with a snapshot of how Joseph Smith prepared it for publication. Instead, it provides us with an unknown number of layers of tampering, potentially over a period of decades.
At some point, someone may have toyed with the idea of what a snout would look like on Figure 6, perhaps having heard that the figure is "supposed" to have one.
In such case, they may have cut into the metal in order to see what it would look like. In support of this theory, we see what looks like an attempt to draw fangs and a mouth, which should not be dismissed, for the same reason the snout itself should not be dismissed. The relevance is not just that it's a snout shape, but that the shape is directly next to the head of the figure. If this shape were located somewhere random on the printing plate, it would be kind of an odd shape but it wouldn't be identified as a snout. Likewise, the mouth and teeth marks are located where someone might expect a mouth to be on a dog's snout.
Fangs would almost certainly have not been on an actual Anubis vignette, but they are consistent with what someone might draw if they didn't know better but had heard the claim that a dog snout was supposed to be there, and decided to experiment. This is similar to my argument that the glyphs in the margins of the Book of Abraham manuscripts were drawn by someone at a later date (except for the Phelps manuscript, which I have shown is a legitimate exercise in Egyptian). What I suspect happened in the case of the margin characters is that Joseph Smith had copied for Hedlock some characters to draw from in making Facsimile 2 and he labeled the sheet of paper something like "For Book of Abraham," which Hedlock would understand the context of but which a different person coming across the sheet of paper years later amongst the other materials would mistake easily as meaning the characters from which the Book of Abraham was translated. The evidence that the snout on the printing plate was altered by a later curious person lends support to my idea of a person tampering with the manuscripts. The ideas support each other.
So, the snout is not likely the work of anyone copying what was on an actual papyrus, but, instead, the work of someone who had been told that a dog snout belonged there.
Moreover, the image does not look like Anubis. Anubis has a flat head rather than a round head and when he has a human body he always wears a headdress.
The shape of the head would be inconsistent with every ancient depiction of Anubis, including the proposed Anubis on this very same papyrus roll, in the lion couch vignette. If the standing figure in the lion couch vignette is Anubis, then a snout of that shape would still be visible on the extant portion, below the lacunae. The snout of Anubis is supposed to protrude out flat from his face, and doesn't point downward unless he is bending over.