Iron and steel - first introduction for coinage

Dear users,
I've been looking for this information online but did not find much.
When was cast iron and steel first used for coinage?
I'd consider these 2 cases as separate.
For steel, the earliest case I found was the German notgeld, but I suppose there could be earlier examples.
And the first officially introduced steel alloy for coinage - was it acmonital in Italy, or something different?
Thank you.

I think we had a thread not long ago were Spartans used iron/steel coins or rods as coinage
my oldest iron coin is from the 1780s

Is that an iron coin of Sendai (Japan) at the end of your photo string?

Yes, indeed