These are all collectible pins. You can buy the collectible pins capsules, or just buy the pins in the Steam Market. Links in the capsule and pin names.
Collectible Pin Capsule – Series 1 (2016)
Collectible Pin Capsule – Series 2 (2016)
Collectible Pin Capsule – Series 3 (2017)
Half-Life: Alyx Collectible Pin Capsule (2020)
