On a sidewalk, an unassuming junction box sits strapped to a fence. Inside, dozens of keychains, stickers, mini figurines, and other novelties wait to be discovered by eagle-eyed passersby or trinket traders who have traveled across the city to exchange their treasures.

Trinket trading has taken off on social media in recent weeks. The trend originated in Philadelphia, where Philly’s Trinket Trove began documenting the contents of a repurposed electrical junction box on TikTok in........

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