South-East-Asian knife quiz

[Sajen]

Here some hopefully better pictures. The brass handle has a enormus patination, it would be a shame to clean it. The crudely worked blade is almost black but has red/active rust as well, I am unsure what I will do. What you would do? The scabbard is old and show aso many signs of long use but could be a later replacement.
I am now not sure anymore that it can be called si euli, a si euli is a knife/dagger but this is formed like a golok and seems to be a working tool mainly. Opinions? Age I would guess end of 19th century/beginning 20th century. I am glad that I see it.
It coming from a household clearance from an old skipper who lives now in a rest home but this is unproved.
I've taken a lot of pictures and will show them all.