Your once in a life time opportunity to get the silver badge for participating in Private Beta, is no longer obtainable after the private beta period ends (7-21 days).
The requirements are:
- 3 posts with a net score > 0,
- Vote 10 times,
- Visited the site on 3 separate days,
- (All of the above need to be completed before the 7-21 day private beta period ends).
27 users got this badge in the last Private Beta to go public (Drones SE). I hope to see a lot of these awarded for us as well!
Credit: This post was almost entirely taken from here.