Dear Collin,
The mandau that I posted for comparisson is collected by Wolfgang Leupold in North East Borneo near the Kayan river.
The white/red/black coloured goat hair is in my opinion quite typical for the kayan and kenyah tribes.
If you check a map with various tribes from Hornbill and Dragon (B. Sellato 1992) you see that kayan and kenyah tribes are neighouring tribes of the Iban.
The leech pattern is found a lot on Kayan /Kenyah carvings but is indeed also found a lot on Iban scabbards and other tribes.
Your mandau may well have been collected in Sarawak (the english provenance being an inportant hint
) but I would not call it Iban as Wouter does.
maybe a matter of different 'mores', different opinions
All together it is a very nice example in prestine condition.
Ps. looking forward to the additional picture of the mask.
Best regards,
Willem