You folks are too fast for me!
Good thoughts all!
Regarding the nails, I have seen them used on older pieces, and what we would consider "crudly" made ones at that. Glue for something on top would not last long. Most plates I have seen use nails. Not uncommon from what I have handled and seen so far. An observation is that from the ones I have personally dealt with, the majority seem to be Maguindanao kris that use nails or wire connectors overall.
The picture I have is the earliest one I have that uses 10k gold over copper nails to keep the gold/turtleshell/mother-of-pearl in place. This kris goes back to around 1900. Only one of the nails shows in the middle (the rest are underneath the middle gold part).
Copper, brass, silver, gold, and swaasa are all materials that have been used on older pieces. When it comes to newer pieces, most do use more copper and brass since these are cheapest (but no guarantee since recent versions of Moro stuff coming from Marawi in Maranao territory still use gold plating and silver). I would say that for the most part swaasa is older since it takes more time and effort to make (made of gold, copper, and a little silver).
It is possible that a guard was modified to recycle on your piece Flavio, but this would also be in keeping with a long cultural tradition (recycling or selling of precious metal parts like silver, gold, or swaasa).
Final note: I think the strap the way is it is interesting.