Alan, please don't interpret my enquiry as a sign that i disapprove of keris adapted to old sheaths. As you must know, i hold many such keris in my personal collection and hold those keris in high esteem. Especially when the re-fit is artfully accomplished. I asked Arjuna you show the fit simply to learn more about this keris, if the sheath is original to the blade or, if adapted, how well and by what methods.
I'm pleased to hear you believe the naga to be original to the blade. I have less tolerance for those adaptations than the fitting of sheaths.