I, for one, feel quite happy in applying a sliding scale when deciding what to obtain for my collection and don't have any criteria written in stone that define what is IMHO legitimate, genuine, nice, untouched/complete, old, etc. and which need to be met by any new family member...
I'd be enthusiastic about any antique high-quality blade (even damaged and/or without any fittings) and may also be more than happy about an antique village keris of fairly crappy quality if deemed a "complete, original combination", from a rare origin, or, possibly, even special provenance. Heck, I may even go for a current era keris if it speaks to me...
From a practical POV, much more relevant than trying to define what makes a keris "legitimate" would be to ascertain that I don't fall prey of any misrepresentations that abound with things keris (from ol' myths/exaggerations like meteoric metal to downright lies and forgeries).
Regards,
Kai