An mc$ file extension is related to the Magic Cap operating system. An mc$ file stores archive.
MC$ file extension - Magic Xchange package (Magic Cap file archive)
What is mc$ file? How to open mc$ files?
File type specification:
The mc$ file extension is associated with the Magic Cap, an object-oriented operating system for PDA devices, developed by General Magic.
The mc$ file stores archive from Magic Cap.
Mime types:
application/x-magic-cap-package-1.0
This mc$ file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.