
The provided search results do not contain information regarding the composition of Singapore's coins. The first source links to an unavailable page from the Monetary Authority of Singapore, and the second source discusses US coins.
Based on general knowledge, the current series of Singapore circulation coins, known as the Third Series introduced in 2013, is primarily made from multi-ply plated steel. The specific composition varies by denomination. The 10-cent, 20-cent, and 50-cent coins are made of nickel-plated steel, while the 5-cent coin is made of brass-plated steel.
The one-dollar coin from this series is distinct as it is a bi-metallic coin. It features an outer ring made of brass and an inner disc made of a nickel-plated bronze alloy.
Previous coin series had different compositions. For example, the Second Series coins, which were in circulation from 1985, were largely made from a cupro-nickel alloy for higher denominations and aluminum-bronze for the lower denominations. The shift to plated steel in the current series was implemented to enhance and manage production costs.


