VMS Help PRODUCT, SHOW, PRODUCT, Qualifiers, /PRODUCER  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /PRODUCER=(producer-name[,...])

    Selects software products that the specified manufacturer
    produces.

    Parentheses (())  are optional only when you specify a single
    producer name. They are required when you specify multiple
    producer names.