Oh well, I wasn't really in the market for another kris

[David]

Originally Posted by Marcus

Clearly, I am not a kris specialist so I could also use help with some of the terminology, specifically Mr. Maisey's statement "Marcus' wrongko is almost certainly sono".

Marcus, i believe Alan was referring to the type of wood used to create this sheath. This wood is known more completely as Sonokembang in Indonesia. https://en.wikipedia.org/wiki/Pterocarpus_indicus
I am not sure what exactly would make this a illegitimate naga keris. Bad execution is not really a measure of legitimacy.
You may never be able to nail down the exact origins of this keris for sure.