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.
The Cobblestone collection would drop to players who held an active operation pass for the duration of operations Bloodhound, Wildfire and Hydra. Skins from this collection have not dropped since the conclusion of Operation Hydra in 2017.
The Cobblestone collection is one of the most famous CS:GO collections for its highly elusive and heavily sought after AWP Dragon Lore.
Since the conclusion of Operation Hydra the supply and availability of the AWP Dragon Lore has quickly reduced which in turn has seen the lower rarity skins such as the M4A1-S Knight rise in price sharply as they are used in trade-ups (typically 10% or 20% chance trade ups).
Usually souvenir quality skins are worth more than their non-souvenir counterpart. However, since souvenir quality skins cannot be traded up to a higher rarity, the M4A1-S Knight in souvenir quality is worth significantly less than the non-souvenir variant.