Skins from The Cobblestone Collection are not obtainable through the weekly drop.
The Cobblestone Collection is a Valve-made collection of CS:GO skins introduced on 1 July 2014. The collection consists of 5 consumer skins, 4 industrial skins, 2 mil-spec skins, 2 restricted skins, 1 classified skins, and 1 covert skins.