I finally finished labeling all of my books in my new Calibre library with where they were purchased. I had to guess on a few of the freebies as I just don't remember. I mostly went by my library at stores plus email receipts. I couldn't find my receipts for the Julia Quinn 2nd epilogues from way back when, but I knew I had purchased them direct from HarperCollins.
It made me realize how much I miss the heyday of Fictionwise. I also am amazed at how many stores have gone out of business: Fictionwise, Books on Board, Diesel, and now Sony. I also had one or two books each from various places back when you would pay and then they'd email you a link with the download

I've been buying ebooks since 2000 and I much prefer the actual storefronts we have now