ABUS 6N keys are common on ABUS bike locks. They typically come with a black plastic head with a embedded ABUS logo.
These keys can be made to code. The code number is usually marked on the key itself or on a separate ABUS security card. Codes are in the format 6N followed by several digits, e.g. 6N 0749.
Simply type in your code number in the box (including the 6N prefix)