Thank you for your reply. The Adobe forum discussion you mentioned appeared much more concerned with protecting a final state in terms of Develop changes. My concern is much broader, meaning I'm concerned about making unintended changes to metadata like Keywords, Star Ratings, GPS data and so forth. Develop changes would also be nice to lock down too.
My thought is that we could select thousands of images at one time, perhaps by highlighting the parent folder for an entire year, and simply "Lock" the files. As an amateur, I'd guess that would be too burdensome from programming perspectives. Having made unintended errors in keyword deletion ad Star rating deletion, this has become important to me. Catalog backup really isn't useful unless you know when and where you made such an error, and in my case, errors weren't discovered for many months after the fact.
Surprised this hasn't come up before.
Thanks again,
John Caldwell