When labeling "secret" information, which designation would you use?

The designation used for labeling "secret" information is SF 706. This standard form is specifically designed for the classification and marking of security information at the secret level. Utilizing SF 706 ensures that classified information is properly identified, helping to maintain security protocols and inform personnel of the sensitivity of the information they are handling.

The other forms mentioned serve different purposes; SF 707 is used for confidential information, SF 708 is for unclassified information, and SF 710 is typically used for non-standard markings. Therefore, choosing SF 706 is appropriate when dealing specifically with information classified as secret, as it corresponds exactly to the requirements for that classification level.