mandau handle for comment

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I have this mandau hilt with motifs that I have not seen before. On both sides of the hilt surface, there were several carvings that Look like little heads/skulls?

Are these merely whimsical decorations or are they also some form of cultural symbols/meanings like lemantek (leeches) or Aso?

The hilt has a good patina and probably quite old.

Can you fellow mandau lovers/experts give comments and also which dayak tribe/region this is from?

Thanks in advance for your comments.