equals(Object other) An equals method that returns true if the other obejct
is a sub-class of this, and the container identities
are equal *and* it is the same class as this.
An equals method that returns true if the other obejct
is a sub-class of this, and the container identities
are equal *and* it is the same class as this.
This allows mutiple additions of value equality
obejcts to the observer list while only retaining one.