It isn't an era-appropriate accessory like some may assume; rather, it's a solid-gold Rolex with a ceramic bezel, a watch that was first manufactured around 2010.
In the next scene, he arrives at his apartment to see his sister, Laura Rosemarie Dewitt.
But by that time, he's wearing a blue shirt, despite not having had the opportunity or time to change.
It was serendipitous how it happened.