Well Alan, as you know, i am merely a student of the keris, but i know even less about tombak. Could you tell us what characteristics about this tombak are non-typical to Javanese origin. It might help Doecon's understanding of why you hesitate to classify this one and it would probably help my understanding of tombaks as well.
Personally i think anyone would be somewhat foolish to claim they can make a positive ID of keris and tombaks based on a few photos viewed on the internet. Photos, even apparently good ones, can easily mislead as to tone, hue and color and give no indication of weight or feel.