There are several types of defects that will affect the value of a comic book, for my own purposes I classify these in two categories, they are Publishers Defects and Handling Defects. I consider defects caused by acts of nature (flooding, fire, etc...) to be handling defects.
So let's talk about the first types of defects, those caused by during the process of printing and binding. The most obvious and for me the most annoying of these is an offset cover, but there are a lot more than that, here's a list of what I consider the easiest to identify.
Horizontal offset: the cover has drifted during the binding process so that the fold line can be seen on either the front or back cover instead of along the spine.
Vertical offset: the cover has drifted during the binding process so that white may be observed at either the top or bottom of the cover.
Progressive offset: the cover has shifted during the binding process so that the fold line can be seen on either the front or back and is slightly diagonal instead of vertical.
Double Cover: one or more extra covers has been attached to the comic during the binding process, while this defect is one of the very few that will not detract from a comics value, it is still a defect.
Staple alignment: this includes staples that are to high, to low, offset, or are canted slightly. Ideally staples should be placed so that from the top of the comic to the top of the upper staple is the same distance as the bottom of the comic to the bottom of the lower staple.
Miscut comics: measure the top of the comic and the bottom, is the measurement the same? If not it is miscut. While not always noticeable to the naked eye, a scanner will pick up this defect very quickly. I have seen people accused of trimming a comic that was miscut. a folded page will also lead to a comic being miscut, as well as adding a crease to it, that is normally considered to be a handling defect.
Corner flecks: A tiny fleck of paper torn from a corner during the cutting process, this generally will happen at the fold, but may happen to any of the six corners of a comic cover.
All of the above happen before a comic is ever boxed or shipped to the distributor and we have no control over any of them, they are also why I tend to believe that there are few if any mint 10.0 comics in existence. Is your comic mint, if you have never opened it, it is possible, but how would you know? if it has any of the above defects (other than double cover) I can guarantee that it is not mint 10.0, but further if you have never opened it how do you know that the pages aren't all blank or even have the right comic in the cove, it is possible that the cover has been put on upside down and backwards or that there is a miscut page due to a fold inside the comic, but because you never opened it you can't know that it is mint. Let's face it quality control is pretty much nonexistent at comic book publishers so it is up to you the buyer to make sure your mint 9.8 or 9.9 comic truly is what you think it is. So do carefully open your comic and check each page to insure that no defects are on them and while you are at it count the pages, if you have 36 or 28 pages when you should have 32 then you know that something isn't right. (pages are on a normal comic (not square or prestige bound) will always be in fours, two leaves per sheet with two sides per leaf.
Next Blog I'll go over some handling defects.
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Again I love all of your posts, great info and perspective. I can accept your rubber gloved reading, but if you do it in a "clean room", I'll start calling you Howard Hughes. I particularly liked your advice on splitting your money between new and old books. The modern print runs are to big, with to many collectors/speculators/dealers taking better care of the books. I have not bought anything in a long time, but have held on to my books, and occaision ally take that trip down memory lane...will change the boards the next time.