Malay keris with very old Javanese blade?

[Sajen]

I came across this Malay keris with an Javanese blade, which seems to my eyes to be a very old blade with 9 shallow luk. When the seller took pictures for me, the scabbard fell down. I took it anyway, of course for another price, fortunately he sent me with all pieces of the broken scabbard and I was able to reglue it passably.
Was it common to refit old Javanese blades in Malay dresses?
As usual, all comments are very welcome!