Welcome to the forum Oriano!
I am not an expert for weapons from Central Africa but I can give you some material for reading!
Here a piece I've owned once, so far I know it's now in the collection of an other member:
http://www.vikingsword.com/vb/showth...light=trumbash
And here a general discussion about an age of these blades:
http://www.vikingsword.com/vb/showth...light=trumbash
For your piece I would guess 1930 or later. A nice piece!
Regards,
Detlef