Here is some further info on the Battle of Bubat.
Of course, nothing is said here about this practice of reversing keris hilts. It is not something i have ever come across in my readings before. Interesting if true, but like Jagabuwana, i believe i will continue to present my own keris with the hilts in their "correct" position.
https://en.wikipedia.org/wiki/Battle_of_Bubat