After reviewing #UsualToken official communications, the staking mechanism involving a 10% unstaking fee and its distribution was detailed in the Usual Staking Module documentation, which was last updated on December 4, 2024.

Additionally, a blog post titled "Introduction to USUALx and its game theory," published on December 17, 2024, provides further insights into the staking mechanism and its implications.

Therefore, the mechanism was publicly detailed between December 4 and December 17, 2024.

For the most accurate and up-to-date information, I recommend reviewing Usual Coin's official documentation and announcements. Here are some resources that might be helpful:

Usual Protocol Official Website: usual.money

Usual Governance Token Documentation: docs.usual.money

Usual Staking Module Details: docs.usual.money

These resources should provide comprehensive insights into Usual Coin's staking mechanisms