Coin/Token Material

I do not have a metallurgical lab to verify the metals in Coins or Tokens. I see coins in the onsite catalog that say "Brass" but I believe that it is zinc with brass plate. My coin the rim edge was worn and below the brass it looks dull dark grey.
1. I think that would be zinc?
2. Should I make a revision change?

I know that It's very common to use steel interiors for coins, for example the 1, 2, and 5 euro-cent coins are made from steel on the inside and have a thin layer of copper on the outside. Steel is cheap as iron is the second most common solid metal in the world after aluminium (although aluminium is also a possibility because it's so cheap). Lithium may be the most common metal in the universe, but iron and aluminium are the most common on earth so to cut costs it's common to substitute the less common copper and zinc for aluminium or steel.

"copper-plated steel" that was the term I was looking for, excuse me, my English is quite bad.

I thank you Trung Quoc Don for your reply. I think that I will submit a revision just saying brass plated and not state the core.

Would not a steel core be magnetic?
These that I think are zinc are not magnetic.