Thanks for your comments.
I agree with your way to differ the Coteng from the Tajong but after reading Spirit of Wood I am confused. Do you have the book?
The Tajong 1 in their evolution of Hulu Tajong is just like a Coteng, even called Tajong 1 Hulu Coteng, but still is described as a Tajong.
On the blade I also agree but can assure you that I at least haven't fiddled with it.
It fits perfect in the scabbard so if some exchage has been done maybe it's a change of only the hilt?
But in this interesting thread I noticed a Coteng (DA Henkel's) that have a similar blade as mine?
So maybe it could be original?