Pierced blade?

[A. G. Maisey]

Why was this done?

No idea, it is not anything that I can associate with any Balinese tradition, so I guess it was done outside place of origin of the keris.

Many years ago, in Queensland, Australia, the Commissioner of Police decided that it was perfectly OK for Queenslanders to keep vicious, inherently dangerous weapons such as keris, provided they did not remove them from either their homes, or their scabbards.

To ensure that all keris remained in their scabbards at all times, it was decided that a hole or holes should be drilled through both the top part of the scabbard and the blade, and a bolt or bolts put through both scabbard and blade.

I doubt that the precision drilling of this keris is a result of that extremely intelligent administrative decision, but whoever did this drilling clearly possesses a level of intellect that could well be compared with that long-ago Queensland Policeman.