I've always been particularly fond of "ringers" and have a few myself that have particularly good resonance. Some writers (Tammens for one i believe) have made reference to different types of rings having different significance. It seems to be a sign of good metal working to me, though many of my better keris don't have much of a ring at all. Interestingly, one of my best ringers is also a Bugis blade, though one from Sulawesi.
BTW, take it for what it's worth to you, but i have heard that it is considered rude to the spirit of the keris to plink the blade with your finger.
Though i must admit i find it hard to resist on a good "ringer" myself.
