In addition to the signs provided above, signs, bulletin board, announcement board or identification signs for schools, churches, hospitals, multi-family dwellings, subdivisions, allotments or other principal uses and buildings other than dwellings on the same lot therewith for the purpose of displaying the name of the institution(s) and its/their activities or services shall be permitted; provided, that the sign shall be erected on not more than one street frontage. Such signs shall be no more than 32 square feet in size and only be illuminated by indirect means.