When building the MARC holdings field for the ABLE bindery client, there is a need for access to the copy number at the item level, not just the holdings level. There are many cases when an item record has a copy number, but the parent holdings record does not.
It would useful to have access to item level copy information in a private field, e.g. _copyNumber. This field would ideally be populated in similar fashion to the _permanentLocation field, so that it returns the item copy number if available, falling back to the holdings record copy number.