Iain, you are far too modest! Your command of the particulars and overall nature of the production and diffusion of the swords of North Africa is stellar!!! Thank you for always adding such great detail and links to illustrate the observations and identifications as well.
It seems that I have seen these 'rondel' type hilts often mounted with 'kaskara' blades and typically classified as Sierra Leone as well, obviously a bordering region and as you have noted the diffusion of these blades was comprehensive throughout contiguous regions along with tribal movements and trade.
I completely agree that presuming native work on blades that cannot be definitively established as European by either characteristic or notable markings is the best policy. I also agree that the 'dukari' or twin moon marks so well known in Saharan blades became well established as a 'quality' device and later applied in degenerated context widely. The 'off center' fullering on this blade seems to be a considerably altered blade of 'kaskara' type, and perhaps the seemingly quite modern scabbard was simply fashioned by a local tribesman to accomodate the piece. It does not seem the work of an artisan who typically carried out such work, the carrying ring is crudely mounted through the braided leather trim rather than in a ring mount or specifically designed mount and the rather industrial metal chape seems roughly fashioned from some type of sheet or scrap.
Colin, I have little metallurgical knowledge, but I have always presumed that these dark patches of corrosion on many of these latter 19th century weapons resulted from the failure of galvanized or other similarly treated sheet steel or industrial metalwork products often used in these blades.
On the well placed note on European trade blades, we only wish there were such literature. While in the latter 19th century, the commercialization of this industry did have some types of catalogs in Solingen for mostly military type swords... the only other type catalogs I have been aware of is in certain cases of smallswords in England and in degree in Europe .
For the most part, blades were simply a commercial commodity which were included with other materials carried for trade, and were not selected or ordered from catalogs. The only material which has lent to tracing the producers of these blades has been the compilations of markings and devices presumed to certain makers, and associated with accord with guilds. These records have only existed in less than accurately documented cases with the exception of some of the records in Solingen. It is a topic which has never been sufficiently researched or published, and in the many years I have been intrigued by it, I feel I have barely scratched the surface
All best regards,
Jim