It could be a backup of a project from 2019 (e.g., "Monthly Materials 2019" or "Marketing Media 19"). 4. Safety Precautions Before opening any unknown compressed file:
Since Windows and macOS do not always support .7z files natively, you will need a third-party tool: MM_19.7z
There are popular plugins like Modern7z 1.9 (often abbreviated as MM 1.9 or similar in archive names) which add extra compression methods to the 7-Zip program. It could be a backup of a project from 2019 (e