Remember?

I found out I could use a magnet to attract a 10c coin or a 50c coin, but not the other denominations.

Then, I tried to find out the coinage material. And the findins are as follows:

10c = 鍍黃銅鋼 = alloy of copper+tin+steel
20c = 黃銅和鎳合金 = alloy of copper+tin+nickel
50c = 鍍黃銅鋼 = alloy of copper+tin+steel
$1 = 红銅和鎳合金 = alloy of copper+zinc+nickel
$2 = 红銅和鎳合金 = alloy of copper+zinc+nickel
$5 = 红銅和鎳合金 = alloy of copper+zinc+nickel
$10 = 雙金屬(黃銅和鎳合金/红銅和鎳合金) inner circle = alloy of copper+tin+nickel; outer rim= alloy of copper+zinc+nickel