Thank you for all the comments!
I am a novice in terms of knowledge about the keris. However, I noticed very often that kerises we see today are in most cases mixtures of different elements and influences, to the point it becomes very difficult to point the origin of a keris. So, we have "Balinese" kerises that are in fact Javanese but in a Balinese dress, we have "Buginese" kerises made in Solo and so on...
So a Sumatran keris with a Tajong style hilt, shouldn't come as a surprise.
Or am I wrong in my conclusion as it is based on my ignorance and a flawed observation?!
PS: I am certain this is a fairly new keris (maybe around 50-60 years old as it was in a collection for the last 40+ years).