Robert, congrats for another great piece to your Luzon collection!
This is the first time I've also seen such blade shape. I drew a line along the top of the blade (pic attached). My speculation thus is that the indentation on the blade's spine is a latter addition by way of a subtraction
As to why one would do that, I can only continue to speculate.
In any case, it's a great blade. And its unique shape only adds mystique to it.
PS - If I were you, I'd just invent a story
-- said
Katipunan bolo was dented by a bullet during a bolo rush, and so the owner being a vain person carved out the damaged portion, and was pleasantly surprised when a sinister-looking blade came out. What would be your version?
