What is the primary function of the tughra created by the Ottoman artist in 1555-60?

The primary function of the tughra, particularly the one created by an Ottoman artist in the years 1555-60, is to verify orders and display the sultan's authority. The tughra is a calligraphic monogram or emblem that symbolizes the sultan's power and legitimacy. It served as an official signature that authenticated documents such as decrees, letters, and other state matters. By incorporating intricate designs and inscriptions, the tughra not only signified the sultan's identity but also communicated his ruling status to the subjects and foreign dignitaries, thereby reinforcing his authority.

While the tughra may certainly carry decorative elements and reflect the artistic achievements of the time, its primary role remains focused on denoting the sultan’s authority and official capacity, which is why this answer stands as the correct option.