Firstly, let me say nice keris. I really like this one. I can certainly see why you are confused though. This is a very unusual blade. I have never seen ricikan like this before. Not only the greneng, but the gandik is also quite unusal. It is, however, very beautiful.
I can see why you made a guess that it might be Minangkabau.The dress seems to lean that way. Though i have never seen a blade like this from there it also has a general stoutness of form that i would not be surprised to see from the region. But i am afraid i can't offer any more encouragement than that.