VMS Help CMS, SHOW, CLASS, Command Parameters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 class-expression

    Specifies one or more classes to be listed. If you do not specify
    a class name, CMS lists all classes in the library. A class
    expression can be a class name, a wildcard expression, or a list
    of these separated by commas.