Question about Kris

[cel7]

Hi, even though I have been on the forum for a while, I have never posted anything in this subgroup. Simply because I have never owned a Kris. This morning I picked up three kris, a tombak and a small parang or something like that from someone who had moved into a smaller house. His father took it with him in 1949 after being deployed as a soldier in the war that the Netherlands waged in Indonesia.
The condition of the sheaths of the kriss is very poor, one is glued and the other is broken.
I have tried to find out a few things myself, but there is so much information that I can't make sense of it. Because I know nothing about the kris, my question was whether it is possible to determine how old they are and whether and how I can best clean the blade. In my opinion they are very dirty.
I also received the folded rug under the kriss and I believe it is also from the same region.

Thank you in advance for your response.