Ever since she was a child, Kathy Waltz of Bow has wanted a metal detector. She got that wish four years ago, and is now an avid treasure hunting hobbyist. On Tuesday, just outside Rollins Park in Concord, Waltz was netting the typical junk – aluminum foil wrappers and can tabs – along with some old coins and what she guessed were small metal vehicle parts. Her more significant finds over the years include a few gold rings and a Tiffany bracelet.