Skin: Happy Skull Scrubs Cap
This skin item is NOT tradable via Steam, but can be obtained by using discovery with the full set a in game.
A special scrubs cap that can be worn or torn into scrap cloth. Right click on the scrubs slacks while they are in your inventory to salvage it which will destroy it and turn it into scraps of cloth.
Gather the full set, and use discovery, to convert into a set of permanent skins.