Monty have you Details on the Box sets ?
I've read bits and pieces of info about them in different places, but I have nothing saved on my phone, tablet, or computer...or, if I do, I can't find it.
The "American" series may be the most popular, and was produced by Rick Rubin, featuring songs like "God's Gonna Cut You Down," "Ain't No Grave," and "Hurt." You can purchase the CD's separately, or in a set.
I believe that "Unchained" and "Unearthed" were both individual albums, but released about the same time. "Rusty Cage" and "One" are two of my favorites from these albums.
I also like some of his classics like "Ring of Fire" and "Walk the Line," but I feel that Mr. Cash's voice improved with age, and I much preferred his later performances of those songs.
I wish I had more details about the albums, but I honestly have never purchased one. I instead have individual songs from various albums downloaded onto my phone. However, a quick Google search of the above titles should answer any questions you may have.