Samuel Clemens' pocket watch is found under San Francisco
A pocket watch is a Terran clock usually worn with a chain fob and carried in the vest pocket.
Samuel Clemens left his watch in an abandoned mine under 19th century San Francisco, where it was recovered 500 years later along with Data's severed head. (TNG: "Time's Arrow", "Time's Arrow, Part II")
The Persistence of Memory, a painting by Salvador Dali, depicted melting pocket watches. The painting was in the possession of Kivas Fajo in 2366. (TNG: "The Most Toys")
Tolian Soran carried such a timepiece with him while attempting to carry out a plan to redirect the Nexus energy ribbon. (Star Trek Generations)
The replica of captain Cray's watch.
In an alternate timeline, Commander Chakotay tried to give Captain Kathryn Janeway a replicated replica of a pocket watch worn by Captain Cray, a sailing ship captain who got his lost crew back home centuries earlier for her birthday. At the time, the ship was under constant attack by the Krenim and she refused it, saying it was a luxury and could've meant a meal or medication for another crewmember. She told him to recycle it, but, unknown to her, he could not bring himself to do so. She found it in his quarters five months later and put it on. Neelix thought it looked handsme on her. (VOY: "Year of Hell", "Year of Hell, Part II")