The Sticker | Greetings is a High Grade sticker. It comes from the Half-Life: Alyx Sticker Capsule.
Sticker
Health (Gold)
Last Vance (Gold)
Big Hugs (Holo)
Combine Helmet (Holo)
Lambda (Holo)
Vortigaunt (Holo)
Big Hugs
Combine Helmet
Gnome Mercy
Lambda
Last Vance
Vortigaunt the Painter