For the missing text, could be possible that it came off or not properly done in the first place.. imo, the workmanship of the brass-works is lacking. Just last month, during my visit to Java, I've seen a few at a 'pasar keris' (keris market). As for the reason for use, it can be many.. for congregations, depending on the need of the user, group or society and for many other purpose. Your guess is as good as mine..
