The Gemini III is designed to locate large, deep objects--like an iron chest, an ore vein or a metal pipe. With its two-box design, it offers much better depth penetration than standard metal detector.

The Gemini-3 is used by professional treasure hunter, prospectors, geologists and public utility employees. Depending on ground mineralization and target size, objects may be detected as deep as 20 feet. A pioneer in the field of metal detector over 60 years ago. Fisher has been advancing the state of art ever since.

The Gemini-3 is Fisher's best two-box ever. If you are a two-box treasure hunter, you probably already know the Fisher Gemini-3 has the reputation for being the best around.

• Detects all metals
• Quality engineered by the oldest and proudest name in the business.
• Sensitive to large, deep objects and ore veins
• Crystal-controlled, 82-Khz transmitter and receiver
• Four modes of operation: Inductive Trace, Conductive a Trace, Wide Scan Inductive, and Narrow Scan Inductive Search
• Optional ground rod and ground plate assembly for long-distance underground tracing
• 60-cycle noise reduction circuitry
• VCO audio target response for precision pinpointing
• Built-in re-charger circuitry for optional re-charger kit.
• Five Year Warranty

http://www.fisherlab.com/hobby/manuals/8703520000%20%28Gemini-3%29%20REV%203%2002.27.14%20-%20Reader.pdf