The dates assumed for Javanese beads are often misstated, because old ideas get repeated as often or more so than later revised dates. When jatim began to appear in the US market in 1983, they were first thought to be as old as "Roman" beads. Then it was suggested they derived from Majapahit times—which would make them about 1,000 years old. Then, it was suggested that they must be even older, because Majapahit iconography never showed anyone wearing these big dramatic beads—so they became "Srivajaya Period" beads. (This conforms to the time you were told.) The most recent information (presented in an article team-written by myself, James Lankton, and In Sook Lee), proposes that the origins of some Javanese glass beads were as early as the 7th century (discussing mosaic-glass beads).

The bead you ask about is a monochromatic glass bead, probably made via a simple folding or rolling technique (manipulating a pad of glass around a mandrel, like closing an opened book), that is subsequently faceted. It's very clear (to me) that these glass beads imitate certain imported stone beads (often quartz crystal) from the Middle East, most likely dating from Sasanian times (from as late as the mid-7th C CE).

These old glass beads are often recovered in a decayed state, and are repolished to make them more attractive. This may easily have been done to your bead.

The contemporary bead industry in Java also makes modern reproductions of these beads, by recycling available glass, exploiting lapidary techniques. They are decent-looking copies, but are far from authentic.

Jamey