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My guess is that "M6G" is a internal or house code number. Unless you know the manufacturer, it is hard to track down.
For example, a four pin "M6G" could be an ADM811, which is a reset supervisory IC.
Are there several of these on the assembly you are looking at? If so, start checking the resistance between the pins. It is common now to put MOSFET transistors in SOT6 packages. They connect the drain to four separate pins for better heat dissipation. If you find four pins have continunity between them, these could be the drain. Then just trace the circuit to see which of the other two pins is the gate.