a sangelat indeed, it has a double djalu memet.
I Dont know exactly what the bright metal insert the bolong means.
I know that manytimes often through the many washings due to the "hormat" = honour given at the keris. The keris gets this bolong at the thinnest places first.
in my opinion there some possibilities:
1. It was there all the time , only this piece of metal (nickel) was more resistent to the arsenic then normal iron, and still stucked there
2.The owner attatched a high value at this keris. rapairing the(starting) bolong with strange iron different than the keris is "not done" , so the reapairing was done with a different metal. Sometimes you see reparations on old kerise done with gold.
3. Its inserted to give more powers at the powers already existed.
in this case i would certainly take this keris to the disco...
....i hope the kerisexperts/lovers can tell more about it