All the comments helped me a lot, but I did not reach a final conclusion yet.
I still hope to find some additional information in old literature or old photo's.

Just popping this typical sewar here in case anyone searches for Sumatra filigree. The work here is very basic and likely added later.

As noted in previous threads, the method is found in many parts of the world.

When I consider the Gunong references and the spear images previously posted, the styles and manufacture methods are found throughout the Muslim communities in larger Asian continent and in particular where the Gunong decorative applications are concerned more broadly, the same material applications are seen on many Jambiya.

Given the hilt style and over all dress of Albert's sword, I'd have placed this regionally as Celebes