Hello Jeff,
Yes, it's a Sumba knife, nice one but not very old. But it isn't a typical West Sumba knife, frankly said I never have seen a West Sumba knife.
The swords from West Sumba have a very specific appearance, see this thread:
http://www.vikingsword.com/vb/showth...ighlight=sumba, see #7.
Regards,
Detlef