So my son was having some fun with his magnets one day, when he accidentally discovered that Singapore’s third series of coins are magnetic. That got my attention and I decided to do some digging. Turns out, the 1 dollar coin has a steel core.

I asked my son to try the other new coins and it turns out that they are all magnetic. This is probably because of a steel core present in the new series coins. MAS source and link

The new series coins are minted on multi-ply plated steel comprising a steel core electroplated with three layers of metals – nickel over copper over nickel for silver-coloured coins; brass over copper over nickel for gold-coloured coins. The new series coins are generally lighter in weight and produce a lower pitch tone when struck against hard objects.