Use tools like ExifTool to look for hidden comments, GPS data, or timestamps in the file header.
The double extension typically means the file was originally an MKV (Matroska) container that was later converted or renamed to MP4 for broader compatibility. The Painter1.mkv.mp4
If this file is part of an online investigation (like those found on Reddit's r/ARG ), look for hidden data: Use tools like ExifTool to look for hidden