: Many budget security systems use a single letter followed by a three-digit sequence (001, 022, etc.).
: Right-click the file and select Properties (Windows) or Get Info (Mac) to see the "Date Created." This often reveals the exact time the video was filmed.
: If you recently offloaded footage from a GoPro or similar device, this is likely a raw clip from your gallery.
: Use a tool like MediaInfo to see the "Writing Library." This can tell you the specific brand of camera that created the file.