[kai]

Hello Detlef,

Congrats for a nice grab! From the auction pics I had doubts regarding the scabbard; from your pics I'd believe it to be old and original Nias - maybe not from the ol' headhunting days but still early collected and crafted within the original culture for genuine use IMHO.

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.

Well, culturally correct would be a polished hilt (brass being a valuable but still economically feasible surrogate for gold which was reserved for storing wealth and status rather than working implements) and a reasonably tidy, unstained (i. e. not etched) blade...
From a tribal collector's POV polishing or even mere cleaning would be a nightmare though. So, take your pick...

Contrary to bronze, brass doesn't polish up nicely (or rather repatinates quickly). So the general collector's preferance to leave brass alone does make sense, especially for long-term preservation. With a strongly patinated hilt, extensive cleaning of the blade would not make much sense either (especially since we don't expect to find interesting laminations). Thus, I'm with Alan and also suggest to go for minimal preservation measures only.

For long-term storage, I believe it would be good to get rid of all active rust though and IMHO it would not hurt to loose a bit of dirt during the process. Instead of WD-40 I'd use some good cleaning oil like ballistol, let the blade soak wrapped in kitchen foil and work repeatedly on the active rust (wooden toothpicks are gentle); when you believe to be done, wipe it dry, take some close-ups with flashlight, and start over again... (Make sure not to touch the brass though!) Once done, a final soak in good mineral oil, removing excess over a few days, and finally wax sounds like a good plan.

The scabbard is old and show aso many signs of long use but could be a later replacement.

To me it looks like good working quality (possibly carved by the owner with limited decoration); the wire does look like a later replacement though.

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.
Here together with my other Nias knife which I would call si euli.

I'm not convinced that these small utility piso would have been called si euli - at least they are a completely different entity/style and worn separately.

Golok Nias seems like a good pigeon hole to assign your piece to until we learn the real Nias name for it...