Your Coffer provides you with steady Gold income if properly used. You can deposit your Gold into your Coffer, and after the duration of 2 hours, you can withdraw the interest along with your deposit. You can't deposit any more Gold while you already have Gold deposited in the Coffer, so please remember to check if there's a shining Gold icon on your Coffer, which reminds you that your Coffer is available now. Upgrade your Coffer to increase the interest rate.
NOTE： Upon purchasing packs of a specific price, you can acquire a chance to upgrade your Coffer. But NOTICE THIS, if you purchase another pack before you use the chance to upgrade Coffer, or you purchase multiple packs, the chance of upgrading Coffer will be unlocked ONLY ONCE! So make sure to upgrade your Coffer IMMEDIATELY after you get a chance!