Swedish medal created for the Stockholm expo of 1897. Unlike others like the Conradty notgelds, this is probably literally crushed coal. I base that on two observations:
a) it says they are manufacturers of coal for electricity and chemistry
b) this has a sparkle that the others do not. That sparkle matches the luster you see on anthracite or similar. This is not easily visible on the pictures but the light specks that look like they might be dust are the lustrous bits.
Porcelain coins are sometimes grouped a such but actual materials used might be majolica and stoneware. There are also the celluloid badge-like 'kapselgeld' notgeld which are more 'coin' than 'note'. I'll try and upload some pictures.....
So, I came across a new one recently although it doesn't come out for about a year. It's a 2021 German 10 Euro coin with a copper-nickel core, a polymer ring and then a copper-nickel blue niobium plated ring on the outside. The business strike of this coin is actual meant to circulate freely and thus would add niobium to the metals used in circulating coins.