Greetings Mykeris,
I was quite delighted to read the post about Raja Bilah's keris (if this is true) as I'm a fourth generation descendant from the Mandailing chieftains who fled Sumatera when the Dutch intervened in the Padri controlled areas. The Mandailing Rajas have a fearsome reputation for being storm troopers in a number of conflicts in the Malay peninsula in the 1840s-1860s, amongst them the Pahang civil war, the Rawa war and the Selangor civil war. In fact, at some point of time, they controlled a fortress on what is now Bukit Nanas in the heart of Kuala Lumpur's business district. I think at some point of time they also burnt the town down
Raja Bilah was the nephew and adopted son of Raja Asal, who together with Sutan Puasa (my grandmother's uncle. For non Malay speakers, my assumed title here, Raja Muda means both the crown prince in Bahasa Melayu as well as a paraphrase of his Mandailing title Sutan Na Poso or the young prince).
He is of the Nasution clan, which is also my paternal clan. I believe there are still a lot of Nasutions actively involved in Indonesian public life, making their clansmen proud.
Regarding weapons belonging to the many Raja of the Mandailings, what I've gathered from my own research is that they prefer big, solid cutting stuff, swords in particular. One of my ancestors Raja Tampian brought to the peninsula a sundang and a pair of spears, now in the custody of an uncle (I have yet to see them or take pictures).
As far as kerises are concerned, from some old photographs a researcher showed me in a book, they prefer the keris panjang of the Minangkabau model. During ceremonies, the rajas are usually accompanied by bodyguards carrying keris in silver repousse covered sarung, usually with the squarish Minangkabau sampir and a rather rudimentary tapak kuda hilt, though I've not seen many keris pendek.
I was told that some of Tuanku Raja Bilah's effects are kept in his mansion in Papan and amongst them some kerises. I'll try and see if I can find out anything about them. If this was truly one owned by Raja Bilah, I hope it has found a good home. I would be a bit disappointed at the descendants for not retaining their pusaka.