Final answer:
Cairo's gift was an antique watch, which relates to the historical significance of timekeeping devices, as exemplified by al-Jazari's famous elephant clock from the Mamluk Empire.
Step-by-step explanation:
Cairo received an antique watch from his grandfather for his 16th birthday. A fascinating example of historical timekeeping devices is evidenced in the work by Syrian author al-Jazari, who created a complex elephant clock. Described in his book 'A Book of the Knowledge of Ingenious Mechanical Devices', this clock showcases the advanced mechanical knowledge and scientific scholarship during the Mamluk Empire. It functioned with a series of chain reactions featuring a whistling bird, a dragon, and an elephant, reflecting the high level of ingenuity in time-keeping devices of the era.