There is no doubt in my mind the marks were applied within Germany. Keep in mind that we are talking about a process which involved a lot of manual labor still, marks were not invariably struck to the same depth or precision.
The fly looks to be dirty to me, also, it is simply not technically possible to strike the mark after the blade had been heat-treated. This would require reheating the blade and destroying the temper. This is why native marks applied to European blades are engraved, they are not stamped.
There is no mystery why these blades turn up in kaskara and takouba, the trade in blades to both Sudan and the wider Sahel we know flowed mainly through Egypt and then, at least for many centuries, Borno was the key distribution point.
The copper fills turn up not only on Kull blades and conversely not all kull blades had them applied. Here's another
http://www.vikingsword.com/vb/showthread.php?t=22651 that is very high quality but a slightly different configuration, perhaps produced a bit earlier.
I think its also imporant to remember that there will always be minor variations in the position of stamps, depth of the marks etc. The same can be observed on a multitude of munitions grade blades including schiavonas that were also mass produced.