Hi Jim !
You raise a fascinating question here, with a very interesting specimen ! The origin of dukari marks on North African trade blades has been discussed on this forum before, if I'm not mistaken, and the consensus went toward the idea that they were locally applied, even on imported blades. However, your example here, the leads suggested by Gavin, and this specimen: https://collections.royalarmouries....ject-31725.html
that I'm adding to our corpus seem to challenge that idea, as we now have two blades that most likely never left Europe carrying those dual dukari marks.
Although it is obvious that some dukari were locally applied in North Africa on local or imported blades, by the means of engraving, some, on the other hand, seem to have been stamped on the metal (as is the case of my takouba, of which I'm joining a close-up of its dukari), and could thus maybe have been marked this way in Europe. I don't know if it was possible to punch a blade this way when it was cold, with the means available in North Africa at the time, or if it needed the blade to be red hot, but I'll try to ask a friend of mine who is one of the most talented swordsmith working in our day (using traditional techniques), as he might have an idea on the matter.