Here are my copies of the 12 volume set of “The History of Middle-Earth”. All are 1st U.S. Edition, hardback copies, published by Houghton Mifflin (some are first printings), and are in either “Fine” or “Like New” condition.
I also have a copy of the Index in The History of Middle-Earth series, but it is for the U.K. publications. My plan is to find copies of these in the future.