20 Francs - Rainier III

Monaco's trimetallic 20 franc coin arrived as part of a broader European experiment with multi-alloy coinage in the early 1990s, driven largely by vending machine manufacturers lobbying for coins with distinct electromagnetic signatures that couldn't be spoofed by slugs. The specification — three discrete alloy bands — was engineered to defeat counterfeiting through conductivity layering rather than precious metal content. France adopted similar trimetallic construction for its own 20 franc pieces in the same period, and Monaco, whose monetary union with France obligated close alignment, followed suit. The series ran only until the franc's effective obsolescence ahead of euro adoption.