The general condition of a collectible document is a main factor of its value. The condition mostly depends on its age, the use of the document and its proper preservation.
About use for example, it is common that movie posters and lobbycards present some pinholes or small piece of tape on a corner, knowing that they were displayed in movie theatres.
It is also common that folded movie posters present slight fold lines, knowing that it is easier to store posters folded, which is fine but can create heavier fold wear if not preserved properly (opened/closed a lot, heavy weight on it, acidity, humidity, heat…).
It is also common that the paper of older movie posers tends to turn a bit yellow with time, meaning that older documents cannot be graded as “mint” document (on our website…), even if they are in a pretty good condition otherwise.
Several grading systems exist to detail movie collecible condition. At www-mauvais-genres.com, we use the "10-grade system", which was introduced by Jon Warren and is patterned after other collectible hobbies, such as comic books. These fit in categories from C1 ("poor") to C10 ("mint"). We do not sell heavily damaged collectibles.
C10 - MINT - Item is "as new" or in the same condition as the day it was made. The item may or may not literally be in "perfect" condition, but it does exhibit an amazing state of preservation with virtually no perceptible flaws of any kind, other than very minor flaws that may have occurred during the printing process. Printing registration should be perfect. In many cases, an otherwise "mint" poster may have printing flaws in the registration, or alignment, of colors causing one color to stand slightly offset from the others. The folding/trimming process should not have resulted in any damage to the item of any kind. Sometimes a poster may have slight fold lines that occurred when the poster was put through the folding machine. If the fold line broke the ink, causing a faint white line, the item should not be grated C10. No edge fraying or dents/impressions are allows in this grade.
C9 - NEAR MINT - Superb. Unused or very carefully used, but with some minor storage defect, minor tear, one pinhole in each corner or some other very minor flaw on an otherwise unused poster. Item may be in "never-used" condition or may have been used in the theatre, but was carefully preserved after use. One tiny pinhole in each corner from being displayed is allowable in this grade. Slightly offset color registration is allowable in this grade. Very slight compression marks (indentations) from move theatre use (i.e. Clamped in a display) are allowable in this grade. No edge fraying. One Sheets, which were normally quarter-folded until recent times, may have very slight fold wear, if such wear does not significantly affect the eye appeal of the image. Folds haven't damaged print.
C8 - EXCELLENT - Commonly referred to as Condition A or Very Fine. Item may be in "never-used" condition or may have been used in the theater, but was carefully preserved after use. If a C9 is almost like new, then a C8 is not far behind a C9. An above-average poster exhibiting minimal signs of use. Bright and clean. Poster has no major defects but could have an accumulation of several minor ones, such as a small (1/8" or less) border chip. No creases on lobby cards, but normal/minor creases on one sheets and larger posters is to be expected. A handful of small pinholes or border tears could be present. Aging on older pieces could be present. Paper could be slightly yellowed, but not brown. Minimal or slight restoration could be present if professionally done. There may be signs of wear and use, such as folds or creases (except on lobby cards), possibly a minor border tear, or pinholes in the border. Not soiled; clean and bright. No frontal tape repairs are allowed in this grade, but possibly one very minor tape repair to the back of the piece. Window cards may have written or printed banners. The image area of the poster should be undamaged. Poster should be bright, supple, and clean. May exhibit more fold wear than a C9, but without significant color loss in the fold areas. A slight amount of color loss is acceptable in this grade, but if the fold wear is such that a heavy solid white line results from loss of color due to wear, then the item would not qualify for a C8 rating. No edge wrinkling or fraying is allowed in this grade. No tape is allowed in this grade. No writing on the front of the poster is allowed in this grade, however, writing on the back of the poster that DOES NOT BLEED THROUGH is acceptable in this grade. Minor tears are allowed in this grade, but they should be MINOR, meaning less than 1" in length, and not more than two total tears on the item. Common areas for tears on posters are at the folds, especially the interior folds where the item may have been unfolded and then refolded. This kind of minor paper separation (tear) is common and is allowable in a C8 grade notwithstanding other extenuating circumstances. Should the item have minor paper loss, such as a small piece missing from a corner or interior fold, it should not be given a C8 rating. A corner crease (1/2" or less) or two can be present, but numerous creases affecting the image are not allowed in this grade.
C7 - VERY GOOD to EXCELLENT - Often referred to as Fine condition. Still a very nicely preserved item. Typically, an item in this grade is almost a C8, but one or two unsightly flaws, or heavier than normal fold wear or pinholes, or small pieces of tape on a corner, cause the item to be assigned the C7 designation rather than C8. Heavy damp stains eliminate the item from this grade. However, a minor damp stain on an unobtrusive part of the poster could be allowed. A window card with the top 4 inch blank area trimmed away should not be rated higher than C7, even if in otherwise C9 condition.
C6 - VERY GOOD - Often referred to as "Very Good" condition or "Condition B." The typical used poster in average condition. A sound example, although with wear and defects to be expected of an item that was intended to be used and re-used. Unusual problems should be described. The poster can have slight browning of paper but not brittleness or flaking; it may also have a small amount of writing in some unobtrusive portion of the poster. Minor border repair, edge tears, stains, or other signs of average use could be present. Eye appeal of the image area should be good. Minor soiling could be present. Larger posters could have minor fold tears (length of which should be described); also normal folds, creases, minor fold tears, possible repaired tear (from the back). Professional major restoration is acceptable in this grade. The poster should be complete and if not, major problems should be described (such as paper replacement). In every case, paper replacement and major color touchup and restoration should be described in detail. Tape anywhere on the poster should be mentioned and described. Small pen markings on the front can be present if noted, but not if large, heavy, or if affecting the eye appeal of the image. Sun-fading on the poster should be described, and if significant, should prevent the example from being in this grade. Heavy insect or rodent damage is not allowable in this grade. Amateur color touchup with colored markers is allowable in this grade. Common flaws that relegate an item to this grade include heavy fold wear, unusually large number of pinholes or staple holes, taped corners or fold lines reinforced with tape, minor tears, possibly minor paper loss (pieces missing) from the edges, edge fraying and so on. Because posters were so often used and reused, the C6 grade is common.
C5 - GOOD to VERY GOOD - A heavily-worn item, showing significant signs of use such as multiple pinholes or staple holes, tape, tears, soiling, pieces missing, small markings or pen/pencil marks. Although this is an "in-between" grade and difficult to distinguish from a C6, items are relegated to this lower classification when there is a greater number of general flaws than would normally be expected in the higher grade, or when one major flaw makes the C6 grade unacceptable.
C4 - GOOD - Below average but still suitable for display. Heavily used, with significant signs of use that affect the overall eye appeal of the piece. Small pieces may be missing from the borders (should be described). Image area will usually have minor defects that may impinge upon the graphics. Could have tape, writing, or tears. Numerous pinholes and resulting tears could be present. Complete, but graphics are face-worn.
C1 - POOR - The lowest grade, representing items in the lowest possible condition. Heavily damaged, possibly missing large pieces, possibly brittle and crumbling. Except for valuable rarities, items in this grade have little or no value.
Information courtesy of LearnAboutMoviePosters.com (Thanks Ed !)