Dear Rand,
The buckle is called Pending in Javanese & Malay. In Malay custom, pending is only worn by palace courtiers. Due to its big size, I would suggest that it was meant to protect the wearer's abdomen from the thrusts of arrow, spears and of course, another keris. The pending wearer will also wear the keris on his left waist to protect his left side of the ribs with the keris's broad sampir .The Malays / Buginese believe that man is short of 1 rib on the left side. I cant provide a link or other proof however, about this as this is another oral tradition's belief
.
penangsang