There is no such thing as a "Mint" comic book. The stresses introduced by the high-speed assembly of comic books by modern printing, binding and packaging machinery inevitably introduce damage. I have many books purchased new 30+ years ago, then bagged and boarded without being read. These books are new and near mint, but can never be characterized as "Mint".

Mint
(CGC: 10-9.8)
(Overstreet: 100-98)
(Abbreviated as MT)

This grade is the most misused of all the comic book grades. Many people want their comic book to be better than it is, but few attain this high of a mark. Those comics that do, especially CGC graded books, can attain the highest possible market value that is out there. This will only happen if there is a market for your comic though. Most copies of Youngblood, West Coast Avengers, and X will never do as well as a highly sought after Spider-Man, Batman, or other mainstream comic book.
For a comic book to be considered, “Mint” it needs to meet the following criteria:
Outside

The Cover
There should be no creases.
The cover should have no fading and look like new.
The comic should lie flat and not roll or have curves.

The Spine
The Spine should be straight with no rolling.
Staples should be like new and not rusted. Inside

The Pages
There should be no tears or cuts.
The color should be bright with no discoloration, or fading.
There should be no stains or marks.
Autographs are acceptable.
Overall:

The Comic should look as if it came fresh from the store.