Paraguay km 177, different metal [решено]

Same coin - Different metal
I have two coins made of what seems to be Copper-nickel-zinc, like the one on the photo in https://en.numista.com/catalogue/pieces4978.html, but I also have a very similar coin (same diameter, thickness, etc) which appears to be made of copper, that I can´t find here in numista. Any help? Thanks.

After being buried in the ground for some time, brass turns black due to tarnish and corrosion.

Цитата: "Cerulean"​After being buried in the ground for some time, brass turns black due to tarnish and corrosion.

​I found one looking like that in Presidente Franco half burried in the ground. But this one look very clean, it's look more like a kind of coating especially if we look at the "A" of Republica ...

In all cases I find this coin very beautiful :-)