In “A Kind of a Stopwatch,” Potts gives McNulty the stopwatch.
The episode aired on October 18, 1963, as the fourth episode of the original series’ fifth season. Richard Erdman plays Patrick McNulty, a relentlessly talkative man who has just been fired and ends up at Joe Palucci’s bar.
McNulty buys a drink for Potts, a strange and lonely patron. In return, Potts presents him with an old family stopwatch. McNulty soon discovers that pressing it freezes everything except the person holding it, turning an apparently ordinary gift into a supernatural device.
The story’s grim twist comes when McNulty uses the stopwatch to rob a bank. He drops and breaks it while escaping, leaving the entire world permanently frozen. Potts is therefore the giver, while Palucci is the bartender and Cooper is McNulty’s former boss. Dingle is not the relevant character in this episode, making Potts the single canonical answer.