Mandau origin based on type of hilts?

[Green]

I know next to nothing about mandaus. This is one of the earliest mandaus that I bought. the blade is simple and heavily pitted . The scabbard has some nice carvings of asos and probably other creatures and vines and the wooden handle is carved probably based on dragon motif?

Can anyone explain where this mandau probably originate from? (eg Which tribe, which region of Borneo)... the antique shop lady mentioned to me it was made by 'orang ulu' in Serawak but she may be wrong because she's not an espert either. And orang ulu just meant people in the hinterland/remote place.

Also, would appreciate if anyone can give comment on the hilt . Which particular Dayak tribe made this type? I haven't seen any like this before until yesterday when by accident I saw and bought a similar hilt (much better and made from antler) at a flea market.