Is there any evidence of a form of non-Arabic writing that was widespread in Western Africa from the Mediterranean all the way down to the Gulf of Guinea?
When it comes to cut down blades and imitations, let me illustrate with a few sboulas I have. The first one is clearly a shortened blade, as you can see by the way the fullers terminate abruptly. It has a script very similar to the sboula Charles posted at the start of this thread, but to me it looks more like a random combination of Ds and Ns than anything else:
Then we have another one which looks like a cut down backsword blade, but may be a native imitation given how the fullers are not perfectly straight. Instead of writing, it has simple dots:
Finally, here is one that sports a flimsy, locally made blade. On that one we have simple decorative swirls:
In all three examples we have something added to the blade locally, ranging from imitation script to swirls to dots. It does not look like pure decoration, and it does not look apotropaic in nature, like the zig zag decoration on the hilts which was meant to turn away the evil eye. It looks very much like a conscious attempt to create a visual resemblance to markings.
I can imagine locals trying to imitate scripts like "Andrea Ferrara" or "Me Fecit Solingen". The artisan who is copying directly from an original may do a decent approximation, but then the next artist is copying from the copy, and so on and so forth. By the time we get to the second half of the 19th century, the 17th or 18th century originals are long gone, and the marking is devolved to what we see on the blades in this thread.
Just my humble opinion on this subject, and I am certainly keeping an open mind, as I have no way of knowing with absolute certainty what these inscriptions are meant to represent.