Jose is correct, it is a bolo from Bicol.
Yesterday I have had contact with Zel by email and this is what he write me:
As for your bolo, it's from Bicol...most likely the Rinconada area. As for age, it looks more modern...WWII and later.
And furthermore:
The type you have is I believed called a sinampalok....I don't have my notes with me right now. Sinampalok is term also used elsewhere in Luzon, but I've heard referred to this blade type in Bicol. I wouldn't get too hung up with the exact name of the blade type. There are hundreds of different blade types in the Philippines and the same blade can have different names even in the same region. What's important is that it's from Bicol...but it's not a minasbad.
When you read this, thank you again Zel!
But it will still be very intersting what Lorenz can tell us/me about this bolo.
Regards,
Detlef