When reading through my Borneo books, I suddenly stumbled over an old photo in a National Geographic magazine of an Iban warrior which is carrying a sword with a similar "lookalike" scabbard as mine.
So maybe I nailed down the origin and call my parang from now on an Iban parang. (as far that it is not a North Borneo sword which was captured by this Iban after taking the poor Dusun dajak's head
).