Yes it is a shared workbook, it is a downloaded workbook as part of a
tutorial lesson.
The symbol at the top of the Changes group can be changed from Protect
Shared Workbook or Unprotect Shared Worksheet.
I have it set at showing Protect Shared Worksheet, so I assume that it may
be shared.
They Unprotect Sheet is still grayed out and it will not allow me to make
changes to the worksheet.