In a csgo manner: Time Sticker means a sticker, that
has date on it (like 2014 or 2016).
These types of
stickers gain value over time, because they become more uncommon, or they even disappear from the Steam Market.
In other way: Time stickers were used sometimes instead of paint in WW2 to mark their guns, checkpoints or even clothings.
Some of these stickers can still exist, in Time
Capsules.
CSGO player: HEY! You got a time
sticker?
OWNER: YEAH, It will gain value over time..
CSGO player: For how much?
OWNER:
Dunno, around 0.20€, but it will be 10 times more after two years.
