You write “You would probably know better than I when it first appeared.”
My only reference for dating is the translation I did of a Sumerian text on a clay tablet. The tablet was safely dated to around 2600 BCE, but my guess is that the information on it is considerably older than that. The cosmic Matriarch is a figure that goes further back than anyone can imagine, and she must have been weaving all that time! Egyptian Neith is just one aspect of the same figure. I don’t think the images of her were originally meant to be taken as a separate entity.
There are several early Sumerian symbols which are direct references to weaving, spinning or related arts like sewing, the clearest being phonetic LUM mentioned in one of my posts here; this is the origin of our loom – it doesn’t get more direct than that. As I said, I don’t have any specific knowledge other than what I glean from my study of the earliest symbols and their meanings. This language, which I believe to be the oldest of them all, was rooted from the outset in sounds linked to the craft. How much more important could weaving be than that?
For sure there were different types of combs for different purposes and they have been grouped under the ‘comb symbolism’ heading. But the Djet comb has the shape of a weaving comb which means that it doesn’t resemble a hair comb. That’s the important point. The closest I could imagine would be a flea comb for the Egyptian cats…but I don’t think so. Although the stories related to other types of comb are of interest, they’re not relevant to the markings on this one or to the reason for placing it in his tomb. A weaving comb wouldn’t be linked to vanity, for example. Nevertheless, the abundant information you offer here will be very helpful in ongoing and future translations.