If you are sitting next to someone snacking down on a tub of buttered popcorn, you might miss important details in Steven Spielberg’s epic film, “Lincoln.”

So lean in during the scene in which Daniel Day-Lewis, starring as President Abraham Lincoln, sits in the dim light of his White House study deep in thought — a man bearing the weight of a torn Union while devising a political strategy to persuade the House of Representatives to pass a 13 th Amendment that would abolish slavery.

A gold watch swings across his desk, cutting the shadows.

Listen closely for the loud beat of the swinging pendulum.

That pure, unadulterated tick is the sound of an original watch that Lincoln carried....