1989, I do have some that were published in the 60's that I haven't decided if I am going to list them. The older ones have two stories to each book with plain cloth covered hard covers.
Are you looking for collectible books? I probably have 8 to 12. They don't have any sentimental value to me, not sure how the would do on Listia. They are in excellent condition, just have a previous owner's name and the date written inside the front cover.