Ian, technically, what you are looking at is a Kachin Dah from the Kachin Tribes and regions.
http://en.wikipedia.org/wiki/Kachin_State
The sword type is from the Hkahku, Nung, Duleng, Jinghpaw and other Kachin tribes and is very well evidenced. There is a historical photo I know of showing a similar sword initially pictured here with a young Nung man, albeit the scabbard carries more yellow pigment.
Rawson's reference, plate 37 in my edition, is noted as being from the Khamti Shan, a region that borders Kachin states. Beyond Kachin boundaries and border states such as the Khamti Shan that Rawson notes, these are very rarely seen and likely the result of raid rather than trade or manufacture.
I do not recall the sword type pictured in Egerton.
Stone, whilst good to refer to doesn't offer any support for what he based the description of figure 4 on but does note specifically the Naga dao sword types as "With no Distinct pommel" so I can see how he grouped the standard demure pommeled sword of his for his book.
Being a traditional Kachin sword the correct term is Dah