Excellent Redline (I like that moniker BTW, reminds me of Redline 6000, old racing days!)......so the axiom should be, 'you shouldn't judge a sword by its scabbard' in the same convention.
Colin thank you for the input, and its great when we can all get together to compare information and ideas. With me as the novice here, I spent most of yesterday digging through every resource I could find to see if there was any sort of potential for regionally or tribally identifying these Saharan daggers.
It seems Briggs (1965) spent quite a lot of time in Tuareg areas, but was geographically mostly in Algerian regions. In his venerable work, he has used a Northern and Southern demarcation for tribal forms of takouba, which, for me at least has proven challenging. It seems hard to apply this to confederations of nomadic people typically moving about over five countries and vast areas of Saharan desert.
One thing I did discover is that the 'Agadez cross' as seen on the left and right examples in the original three posted here, is indeed that known as 'Agadez', but it is one of 21 cross forms, each attributed to other primary Tuareg locations. I found that Agadez (in Niger) was a kind of key point or center in a sense, and for example, the green leather used in scabbards was apparently produced there, and traded for use through Tuareg networks.
The Agadez cross seems prevalent symbolically on many of these daggers as well as on the Tuareg camel saddles.
The other forms of cross seem to be used primarily on jewellery, and not as I presumed in other hilts, though the center dagger here seems to be a variation of the Agadez with arms splayed upward.
Trying to find consistancies in the elements of these daggers, in comparison to other examples I found, it seems that splayed arm configuration may be most aligned with 'Northern' types, from Algerian regions into the Fezzan regions of Libya. I would say this categoric area must include northern Niger as well.
It seems clear that the 'arm daggers' are but one prevalent form of Tuareg daggers, and that that characteristic feature seems to predominate in those areas. The other type, more of a belt dagger resides congruently but more in other areas perhaps .
Turning to scabbards, while we agree these must be a secondary classification feature, one thing I notice is the distinctive open loop on the tip of the scabbard. These seem to prevail on Hausa or Nupe weapons in the same 'corridor' from N. Nigeria into Algeria and Libya.
It is tempting to think that the 'arm ring' form of telek is situated more to Algerian, Libyan, and Niger regions as the same feature is well known on much smaller daggers worn in the same manner as Sudan. This is of course by free association and realizing such arbitrary assumption is easily defeated, however worthy of note.
Naturally most of what I am observing is from research hoping to learn more on these Tuareg daggers, and I look forward to your thoughts as well of course as hoping for Iain to join in. Its fascinating to learn more on weapons I have known little on, and I appreciate the knowledge you guys openly share here.