I’ve never really stopped to wonder how high-end vintage sellers source their wares, but fortunately, reporter Justine Harman has. After a chance encounter at an East Village shop piqued her interest, Justine went way, way down the rabbit hole — or is it a mine shaft? — with a couple of elite denim purveyors, unearthing this story of a prized pair of 19th-century dungarees and the turf wars over authenticity that emerge when an item’s real value is tied to how good a story you can tell about it.