Filenames with this specific alphanumeric structure often belong to one of the following categories:
Specific case studies or lecture recordings used within university or hospital database systems. HMN-219-MR.mp4
Automated surveillance systems often export clips with similar timestamped or serialized IDs. HMN-219-MR.mp4
If you have more context—such as the of the video or the source where you encountered the name—I might be able to help you track down more details. HMN-219-MR.mp4