Frames that are suitable for use as safety glasses must have "Z87" stamped on the:

Safety glasses are designed to provide protection against impact and other hazards, and they must adhere to specific safety standards set by the American National Standards Institute (ANSI). The "Z87" marking indicates that the frames have passed rigorous testing for impact resistance and are thus suitable for use as safety eyewear.

For eyewear to be certified as safety glasses, it is required that the "Z87" marking be visible on both the frame front and on both temples. This ensures that the user can identify and verify that the glasses meet safety standards from multiple angles and views. By having the marking on both components, it is assured that the entire frame is compliant with safety regulations. This also helps in maintaining the integrity of the safety certification throughout use and ensures both sides of the spectacles are equally classified as compliant to the standards.

While other options may address partial markings, only having the stamp on either just the frame front or one temple would not fully guarantee that the entire piece meets the safety requirements. Therefore, the correct and most robust answer is that the "Z87" stamp must be present on both the frame front and both temples.