Even if a code appears on an overseas coupon list, that does not mean it can be used in all services, including Korea. It is best not to judge compatibility from the code string and the original language alone.
Check the Service Region First
Check which service the notice is for — Korea, Global, China, Japan, Taiwan, and others. Even if the same reward or a similar code is introduced, the applicable servers and account conditions may differ.
An Undisclosed End Date Is Not the Same as Being Usable
The mere fact that an end date could not be found does not confirm that it is currently active. Distinguish between material confirming an actual redemption and a record that merely remains on a list.
Time Zone of a Reported End Time
Dates in overseas sources may carry their original time zone. If there is a value converted to Korea time, check it together, and see whether it is an official end time or a report from another publisher.
This Site's Display Criteria
Coupon Collection displays the service region, reward, reported end time, and the date the source was rechecked. Codes not redeemed in the actual game are marked as actual redemption unconfirmed. End records can also be looked up separately.
A failed code does not necessarily mean a typo. Check regional restrictions, deadlines, per-account usage history, and prerequisites, and it helps to record whether it succeeded together with the region actually used and the confirmation time.
Translated from the Korean original. Check the original service region and verification dates.