how to improve it.
When we moved to AACR2 (slightly before my time!) we made a conscious decision not to amend our records, so, for example, editors remained as 100s, even though in AACR2 editors became 700s. Are changes like this 'improvements'? I guess they are if the latest standards are created with the best possible of intentions, but since most (if not all) online catalogues and discovery systems search most (if not all) fields in a bib record, then the customer will find the resource they need, I guess.
As to how to identify such records, this seems a bit more tricky. Our management information system does all sorts of whizzy things, but is unable to interrogate at MARC field level. Well, actually, I suppose that's not quite true, but sometimes it's difficult to put a business case to our IT department about the importance of this when they have a million and one critical processes to deal with.
Often, we upgrade records as and when we come across them ...
Lynne