To come back to the piece; how about dating the Tabak? I would place it as early as 1830.
Leather; I have been in the Phil. many times and have collected and studied mostly Northern Phil. for a long time and actually dont know of any leather made in the Philippines. Most 'beef' products besides horn is mostly imported to my knowledge. And to make the cows'hide soft it would need to be worked with soft acid; this proces is -as far as I know- not (much?) done in the Philippines. Although indeed quite some carabau's are slaughtered (in the past) I got no idea what happened to the hides; in 'igorot country I do not know of one leatherproduct (besides Ilongot packpack).
>Battara; what sort of products (of leather) do you know of? (I could be overlooking something
). Also with the very moist climate its really not 'functionable' to use leather overthere.
Ironworking; actually I also am of the opinion that ironworking (melting etc) has been done mostly after 1800 in the Philippines. Ofcourse this thesis needs a lot of research and prove. My personal knowledge (and research) did not cover so much of South Philippines, have to say. But thats why I post it here. I do not know of many pieces that date BEFORE 1800. I believe the ironsmithing in the Philippines has origins in mostly India and perhaps China.
Coming back to Sajens' Tabak; this is why also perhaps one used files to temper them into knifes.(?!)