The sign name is Supplementary sign 1060-31.

This supplementary sign is used in conjunction with other traffic signs to provide additional information about the rule or condition being indicated. It typically specifies the duration, scope, or specific conditions under which the main sign applies.

For example, if you see it alongside a speed limit sign, it might indicate that the speed limit applies only during certain hours or days. The presence of supplementary signs helps drivers understand details that are crucial for safe and informed driving.

If you have any specific traffic signs you would like me to explain or any further questions about German traffic rules, feel free to ask!