Rick Pressl burst into the board of trustees meeting, a boyish exuberance overcoming his normally reserved temperament. The retired fire chief pulled aside Tanya Sulikowski, the executive director of the Schiff Natural Lands Trust, to show off a rusty, barely recognizable object. It was a Revolutionary War era stirrup, Pressl said, his first major find while excavating the nature preserve. He would soon have much more to show the board. This summer, he and a few students from Ridge High School, unearthed spoons, tongs, nails, horseshoes and several other historic artifacts. The group also discovered a set of four brass...