Isn't the "Free-Storage List" in section 4c, starting on page 26, a mark & sweep collector? They didn't use the term then, but I think it describes one. I'm not aware of any earlier publication.
The paper only has 12 pages, but there is a section 4c with that title starting on page 192 of https://dl.acm.org/doi/pdf/10.1145/367177.367199, and you are correct that it describes a mark-and-sweep collector. I was mistaken, and I appreciate the correction.