5 Sen

Riau was a short-lived Indonesian provincial currency experiment — Jakarta authorized a separate coinage for the Riau Archipelago in 1962 primarily to counter smuggling and the black-market circulation of Singaporean dollars along the island chain. The series was withdrawn in 1964 when Indonesia's Konfrontasi policy made maintaining a distinct border-zone currency politically untenable.

The entire Riau issue is scarce in any grade. Circulation was geographically confined and the series lasted barely two years before all denominations were demonetized and replaced by standard Indonesian rupiah.