The Planet 4546B Postcard is a collectible item, not useable in-game, on Steam. It features Planet 4546B.
The item itself. (Image from Steam.)
Obtainability[]
It was obtainable from the 2018 Steam Awards, now only obtainable from the Steam Community Market and Steam Trading.
Item Description[]
To celebrate the 2018 Steam Awards, Alterra Corporation is offering tickets to a romantic offworld getaway. Escape to the tranquil turquoise ocean of Planet 4546B, a peaceful ocean world.
Gallery[]
The Postcard (image from Steam)
The Postcard's Steam Overview