SHORT: Aqua Magnetic Locator

Introduced in the mid-1950s by the Aqua Survey & Instrument Company of Cincinnati, Ohio, the Aqua Magnetic Locator was a type of dip circle or dip needle magnetometer designed to locate buried ferromagnetic infrastructure like water pipes and manhole covers. It incorporated various refinements over classic dip circle designs to make it more sensitive and convenient to use in the field. Mansfield Water Finder video:    • Mansfield's Patent Water Finder: a Well-Cr...   SOURCES https://patents.google.com/patent/US2... https://www.ebay.com/itm/157791791969 https://physics.kenyon.edu/EarlyAppar... https://ethw.org/Dipping_Needle https://www.prc68.com/I/Aqua.shtml