kai,
i think i found a brother for your piece. i believe it's the same one i have on this thread:
http://www.vikingsword.com/vb/showthread.php?t=1699
as far as subculture, i doubt if it's a tribal weapon per se; the question would be from what province it came from. i guess the term
itak would suffice. here are some close ups. tho the blade shape is different, the handle is strikingly similar, and yes, mine is made out of carabao horn.