According to the book of Evans about North Borneo tribes, the "podang" he is calling a "pedang" was used also in North Borneo (Sabah). There is also a pic of a man carrying a "podang" with him.
Also the Ibans, as already known, liked this sword to be handled.
Evans is saying that "probably" these blades were made in Brunei. This State lies between Sarawak and Sabah, so in my opinion this could be true. Does anyone has read other information written about it?
Dinggat, you should buy yourself the book "iban art" from Heppell. It is a very nice book with nice pictures (You can also see this "podang" in it.)
PS. the dayakswords your grandmother has in her house looks like the real thing. You can see already there the difference in used ones (grandmother), and not used ones (not included your "podang" as Willem already said).
Regards,
Maurice