Excellent craftsmanship on this sort of pedang, with a gorgeous blade. The dark looks more to be patina than 'a wash', though as Kai suggested, I have seen these washed to highlight the inlay.
If I were a betting man I would say the inlay was done within the last 50 years and far younger then the sword. The Arabic makes it somehow seem Sumatran to me, but of course it could have originated in so many places as these styles were supremely popular.
Congrats on a truly nice pick up!
Please see:
http://www.vikingsword.com/vb/showth...umatran+swords