5 Pa'anga

Tonga's switch to polymer for this denomination reflects Note Printing Australia's long-standing regional dominance — the Craigieburn facility has supplied polymer currency to Pacific island nations since the 1990s, partly on the strength of the substrate's performance in humid, salt-air environments where cotton-paper notes deteriorate rapidly. The P#51 designation places this squarely in the current redesign series, which updated the full range of Pa'anga denominations through the early 2020s.

The clear window is integral to the polymer base rather than applied separately — a distinction that matters for authentication, since delamination around inserted windows is a known vulnerability in some competing polymer formats.