Hello Sire,
Inspecting your account, you have received the Postmaster Sterling Treasure.
This can be verified by viewing your Grimoire. Opening the first Postmaster Sterling Treasure unlocks the "Chroma" Grimoire card.
You may earn 3 per week after the Weekly Reset. This is account based, not character.
1. One will be delivered to Postmaster. Players are required to sign in on the given week, or inspect their character via Bungie.net or Destiny Companion App
2. Completing one Weekly Crucible Playlist Activity
3. Completing one Level 41 Prison of Elders Activity.