While "J&M123" is not a standard system file, similar naming conventions sometimes appear in specific contexts:
: Modded or compressed game files (like those for Jet Moto or other retro titles) sometimes use "J&M" or similar shorthand in archive names. J&M123.7z
Knowing if it is a personal backup, a game mod, or a professional document would help identify its intended "text." While "J&M123" is not a standard system file,
You can use 7-Zip on any computer, including a computer in a commercial organization. You don't need to register or pay for 7-Zip. 7z Format - 7-Zip 18 Documentation a game mod
: You can often right-click the file and select Extract All or use the open-source 7-Zip tool to open it.