Originally Posted by Madnumforce
because this kind of folded tang is very often seen on French billhooks,
The issue of patina aside, I note that tangs folded over the pommel at right angles is an aspect of tool construction not restricted to parts of Europe. I've seen it on any number of native-made bush knives and agricultural implements from SE Asian and Far Eastern cultures, and the practice spills over into tool designs modified for use as weapons as well. It's almost universal on the handles of kitchen utensils and knives from China and Vietnam as well. It's a practical and simple assembly method, albeit lacking in visual elegance. Looseness in the grip caused by wood shrinkage is very easily remedied by tapping the bent portion of the tang with a hammer until it seats tightly again.
I wouldn't be surprised if this system was used in parts of Africa as well; I am not familiar with the material cultures there so perhaps other forumites can address this.
The point is that, considering the nascent Portuguese empire's exposure to African and Asian cultures in the wake of the early voyages from the Atlantic and across the Indian Ocean to the East China Sea, there are all kinds of way that various aspects of material cultures encountered along the way could have been adopted. Also significant is the fact that the Portuguese utilized the resources and labor of local craftsmen wherever they went to provide the tools and infrastructure needed to further their conquests and colonial endeavors.