The Fisher Gemini-3 metal detector was introduced in 1988 and is still in production. It is worth mentioning that the Gemini-3 is a direct descendent of the 1938 Fisher Metallascope or "M-Scope", the first ground penetrating metal detector to receive a patent. The Gemini-3 is a "two-box" metal detector that is designed for finding large objects at depth. Two box detectors are not sensitive to items much smaller than a baseball, but can detect large items like a 55 gallon drum or water main to de