ABUS E6 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 E6 followed by several digits, e.g. E6 20660.
Simply type in your code number in the box (including the E6 prefix)