Copyright tracking best practices & browser proxy identifier

PNDPermitting

I was recently asked to provide a reference package to accompany a public notice document for online publication. I built my library primarily for personal reference and a large majority of the content is public domain, but some are journal articles that I access via an institutional login. Since I haven't been tracking which these are, I'm a bit at a loss of how to go back & identify those I can't share. Any ideas?

Is there any metadata flag or identifier automatically added when the Chrome plugin uses my library proxy to access content?

PNDPermitting

I see that I'm able to find at least some of them via the captured URL or DOI by searching on "proxy". I'm not sure how consistent this is yet, but it's a start!