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 & II")
Tolian Soran carried such a timepiece with him while attempting to carry out a plan to redirect the Nexus energy ribbon. (Star Trek Generations)
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. (VOY: "Year of Hell", "Year of Hell, Part II")