i finally managed to take off the mendak from the hilt. not me exactly but this is how it happened. I brought the keris to a few keris and scabbard and hilt makers here and many were of the opinion that it is either ivory or antler but all said to confirm it i had to take off the mendak/pendokok.but nobody wanted to try to take it off....until yesterday when i met one master carver here.
i explained that the mendak is glued to the hilt, he took one look and said sure it can be taken off and proceeded to use brute force without even by your leave

and i was worried sick that he would tear off the delicate silver mendak but walla! he did it without any damage to the mendak... the glue was so dry and old that a strong force did manage to pry it off. but i wouldn't reccommend this method to anyone and i probably won't show any more keris with glued mendak to him
here are the photo of the end of the hilt and he confirmed that it is indeed ivory. an old ivory. So i'm pretty pleased....
but if any of you have a dissenting opinion i'd be happy to hear it.