[Jim McDougall]

Ed, thank you for this thread, and one of the greatest of the 'cold cases' on North African broadswords, the marking we enthusiasts of this field have dubbed 'the enigma'.

While it seems most of the notes I have handy at the moment go back to 2010, this has been a topic I recall further back into the 90s as far as my own involvement in it.

I think right out of the gate here, it is important to note that most of the discussions/queries concerning these marks seem to be from examples found on the blades of kaskara. As noted in the plates you show, from Briggs, 1965, which has been pretty much a Gospel in my own studies for decades, the examples shown are from Tuareg chiefs who were involved in the Kaocen Revolt against the French in 1916-17 . These were 'central type' takouba's and were, in the cases of Adember and Raidera both captured from these chiefs in Agades.

Briggs suggests that these may be native copies of European blade markings as also seen in the plates, with the versions of the cross & orb being interestingly of the gestalt of these curious markings, which are of more bizarre character. These 'enigma' are seemingly almost 'protozoan' looking or as if Picasso's rendition of an octopus.

The issue is trying to find some sort of commonality or common thread to determine possible symbolism. There have been numerous suggestions from far fetched to reasonably plausible through the years. One very good observation was a reasonable similarity to an Ottoman 'toughra', but this still falls too far outside the box in my opinion.
Briggs' suggestion of closeness to the fly, or perhaps the doll, also seem reasonable, but again the stylizing is too removed, and even native copies of various images are more recognizable as to what they represent.

I think the closest possibility would be associated with the varying types of crosses, known as the cross of Agades, of which there are at least 21 variations. These mostly have the circular feature in degree as well as the extensions, and seem prevalent in Tuareg material culture. These kinds of crosses have significant symbolisms and meanings, but seem most likely talismanic in the way they are used in so many ways.

The next question would be, if this is a type of talisman or symbol keenly used in Tuareg culture, then why are these found on kaskara blades?
In Briggs, he notes kaskara examples which carry the dual crescent moons which are found typically of Tuareg 'takouba (these marks are termed dukari).
On p,89, he notes that the Hausa, who were the nomads from Nigeria who were known for blacksmithing appear to have furnished blades not only to the Tuareg of Saharan regions, but to the Sudanese. It seems they had remarkable sources for trade blades, and furbished them according to the requirements of tribal groups they were in contact with.

These 'enigma' seem to have been a fairly recent occurrence on blades, and Briggs notes these c. 1878 in Ahaggar, and in his plate XXc, the sword of Rabidine, a noble of Kel Rela Tuareg in Ahaggar had a central type takouba with this style marking on both faces of the blade.
Obviously the swords with the mark also shown in the plate are from 1916-17, so late 19th c. into early 20th seems the extent of the period known.

However, according to my notes, Ed described this mark on the blade of a kaskara of Mohammed Salin Shangiti, who was Grand Master of the Grand Lodge of Egypt who received it February 1961. It is most recently known at the library of Khartoum. It is unclear the vintage of the sword or its blade.

While the talismanic or other symbolic properties of this marking remain unknown, I feel the most likely place to establish this would be looking further into the variations of the 'Cross of Agades". One of the key sources for this may be the book "Africa Adorned" by Angela Fisher, which is largely on jewelry and has interesting section on Tuareg examples using these crosses.

Just as seen in Briggs, the swords of the Tuareg and those of the Sudanese may remain separate in form, however the blades and marking are often closely diffused.

In the pics, a 'Kasallawi' style kaskara, but believed of earlier period , c. 1914-18 in form favored by Ali Dinar in Darfur. Note the marking which has been seen on a number of examples, and is also often regarded as a variation of the enigma, despite being more like the European marks copied.
The takouba is from Lee Jones article and illustrates the 'central type' of these, with the blade form most commonly seen, with three fullers and the twin moons (dukari)....these blades termed 'masri' and according to Rodd (1928) were typically regarded in those times as Hausa sourced.