Welcome to our forum, Godfried!
You definitely are located in the best country for collecting Dayak pieces!
Albert started with some classification approaches for motifs in his recent book "Traditionele wapens van Borneo. De uitrusting van de koppensnellers. Deel III, zwaarden en messen" - I'm sure you have this resource. Still lots of work needs to be done due to the overwhelming diversity (not to mention migrations, cultural cross-fertilization, and influences from coastal Malay communities including truly international melting po(r)ts like Banjarmasin).
Finding names will be tough and likely change a lot from one settlement/clan/culture to the next. It might be much more relevant trying to identify the origin of a mandau first - if feasible. This certainly needs detailed discussions (and lots of pics from all angles for each piece).
Some of our core contributors on things Borneo have participating a bit rarely in recent times - maybe posting some good/interesting/variant pieces gets them out of their caves eventually...
Regards,
Kai