With Mac OS 8.1 installed, when I double-click the System suitcase, the Finder displays an error message stating that the file is damaged.
This is caused by having Appearance Extension version 1.0.2 installed. Mac OS 8.1 installs version 1.0.1 and Mac OS 8.0 installs version 1.0. It is important to note that the System suitcase is not damaged.
Solution
If you need to add or remove items from the System suitcase, you can do this by using the following workaround.
2. Open the copy you just made and make the changes.
3. Close the window for the copy.
4. Drag the System suitcase from the System Folder to the Trash.
5. Drag the copy from the desktop to the System Folder.
6. Make sure the System Folder is blessed by making sure the System Folder icon has the Mac OS logo on it.
7. Restart the computer.
8. Empty the Trash to delete the old System suitcase.