Unique Code Field

Adds a new read-only Unique Code type to Drupal Fields. This field can be assigned to every entity.

How does it work?

This field will be pre-filled with a randomly generated code based on the settings provided by the User.
It will automatically perform a check to ensure that the code is unique in the field parent entity.
The user can choose between these types of code:

Source: https://drupal.org/project/project_module/feed/all