.2mg is Apple IIGS Disk Image
Key Features: .2MG File Extension
What is an .2MG file?
Disk image created from a floppy disk formatted for the Apple IIGS, a 16-bit Apple II computer; may contain applications, games, or other files that can be used by an Apple IIGS system.
2MG files are also recognized by various Apple IIGS emulators, allowing them to be opened on newer Macs, as well as Windows and Unix systems.