Duit Holland [solved]

I was browsing this issuer when I noticed two different pages sharing the same pictures :
https://en.numista.com/catalogue/pieces8575.html
https://en.numista.com/catalogue/pieces68039.html

According to NGC, the pictures used on the numista page is for the "silver" one (KM 80a) : https://www.ngccoin.com/price-guide/world/netherlands-holland-duit-km-80a-1702-1768-cuid-1084268-duid-1432345
The "copper" one : https://www.ngccoin.com/price-guide/world/netherlands-holland-duit-km-80-1702-1780-cuid-1112274-duid-1433758

However, I'm wondering if there is really two different types : I don't understand why they would have put in circulation silver and copper coins with the same design and face value during the same period...
That doesn't seem to make sense !

I'm wondering if those coins are not made in billon : that could explain why some of them look copperish and why some other have a silver aspect instead.

I cannot explain why, but they had very interesting doubling of coins with the same nominal value. For example:

Indeed.
That would be great if we have the weight of the silver coin as the copper one as a billon aspect.

Anyway that doesn't change the fact that the pictures showed on numista for the silver and the copper issues show the exact same coin : that doesn't help to differentiate both issues

i'm a Dutch collector. I have almost all the years at 3 years not. I can dilever a better picture of copper one!
Greetz from holland

The copper coins were the normal circulation coins. I think the silver and gold strikes were trial strikes.