50 Seniti - Taufa'ahau Tupou IV FAO, magnetic

The FAO series coins were issued under a United Nations Food and Agriculture Organization program that encouraged member nations to mint coins carrying agricultural themes as a form of public education — Tonga participated across several decades. The switch to nickel plated steel for this type reflects the broader Pacific regional trend of the early 2000s toward cheaper magnetic alloys as rising nickel prices made solid cupronickel increasingly uneconomical for high-denomination circulation coinage.

The magnetic variant is distinguished from its cupronickel predecessor, KM#71, by the steel core detectable with any pocket magnet — a useful field test given the two types are otherwise dimensionally identical.