은 열쇠 that grants 하나의 렌즈 석

A silver key guaranteed by the Event NPC
You need this item to open
the Silver Treasure Chest dropped by a Monster

With the Lens Stone that you can get with free coupons,
you can improve your Damage and Cast Time

Only 1 free coupon is provided per account even if you buy multiple silver keys
Coupon issued on: 6:00 pm, Friday, July 6, 2007
To see the coupon: Go to the 'My Coupons' menu on the official web site