Conde Nast Publishing was one of the few firms that systematically renewed their copyrights as the successor publisher of all Street & Smith Titles, including The Shadow, Doc Savage, and The Avenger.
In the mid 1970’s, they still had a gentleman on staff who was tasked with renewing copyrights as they came due and would authorize Fan publication appearances of those 3 characters, if asked.
Commercial projects had to be licensed but they understood the value of not harassing fan-publications.

An incredible number of comic books published in the 1950’s never had their copyrights renewed, and now huge numbers of them are in public domain and subject to reprinting.

See here for available titles. They take original issues, scan them, and reprint them.
https://www.psartbooks.com/

Thanks for the reference. Bookmarked the site. It looks to be a rich vein.

More lousy horror movies. That is all. That’s enough.