Thanks for adding the pic!
The auction house didn't gave any support for their estimate - with them confounding horn and bone, I don't see any reason to put much trust in their descriptions...
The blade is quite nicely done, indeed. However, it does show the flow of lines and details of later rencong; also note the forging flaws at the bolster. It may predate WW2 a bit - however, much more important is that it does appear to be made by an Aceh bladesmith.
BTW, the Chinese/Malay souvenir industry in Medan was already in full swing by the late 19th century! I'm pretty sure the fittings were done there (post-WW2).
Still, the genuine blade certainly makes this later example collectable.