[David]

Frankly, that is a good question Carlos. I do see keris like this from time to time and i believe there is an example of this type of dress in Frey's book, though he doesn't have much to say. They do always seem to me attributed to Borneo. The question in my mind is whether this is a legitimate ethnographic dress for a particular tribe or merely a touristy thing. It is certainly a very "primitive" approach for keris decoration. Also, whenever i see these both the dress and the blade are always in poor condition, as if they came from a culture that doesn't take the usual ritual care of their keris.
My guess would be that both the blade and the sheath were made in Jawa and ended up in Borneo as trade to be decorated locally.