Consider the multi-component object.  In the paper paradigm there was one card for an entire series of related objects.  The tall-case clock and all its various components was given a number 972.15.1-14.  In the new digital world order, the relationship between the parts is less clear.  The metal components have been stored in the dry vault, the case is in the furniture storage area and the face is in the lab for conservation.  Another example is the dining room set with 12 chairs.  They are related by number, but there is only room for 4 on display in the gallery.