Besides the normal wear and tear the comics have been subjected to over the course of seventy or more years, many comics were subjected to a process known as stripping. In the 1940's and 50's when all comics were sold at news stands and drug stores, the retailer didn't have to return the whole comic to the distributor to get credit for unsold issues. All he had to return was either the front cover or the title strip(this is how you get 3/4 cover comic books) from the comic book. In theory after "stripping" the front cover or the title strip from the comic the retailer was supposed to throw away the rest of the comic. In practice, however many retailers sold the remainders to used magazine stores or used book stores to make a little extra money. Many of these stores had vast piles of these coverless, and 3/4 covered comics. so when comic books became collectable in the early to mid 1960's they started selling them to collectors. I remember one such place "Stan's Magazine Exchange" in Brocton Mass. They offered coverless comics for .50, 3/4 covered comics for .75, and comics with full covers from $1.00 to $5.00. This was 1965 of course. My 12 year old fan-boy self couldn't resist and I once ordered a big pile of coverless comics from "Stan". These days I can only recall two of the comics I received. Sun Girl # 2, and Star Spangled #68. Any way that's why there are so many coverless comics around today.
