Condition is particularly important for valuable stamps.  Stamps are delicate creatures, and especially for classic material, few pristine examples have survived.  For some collectors, condition is a matter of connoisseurship or pride of ownership, and many stamp collectors seek stamps in the best condition available (or within budget).  This devotion to condition may even cause a collector to upgrade a stamp to a higher-condition if a better example comes along.

As with all other parameters of collecting, YOU set the standard for what you collect.  If damaged or less than pristine stamps are not objectionable to you, feel free to collect them – just keep in mind that a damaged stamp has much less value than a perfect example both when you buy it and when you sell it.  Stamp collectors look at a variety of factors in valuing stamps:

Freshness:  Stamps should have bright color and not be stained, faded, smeared or toned.  

Centering:  Especially in earlier material, many stamps have designs off-center or impacted by the perforations.  All things being equal, most collectors prefer stamps with large and even margins around the edges of the design to stamps with small or uneven margins.

Cancel:   Used stamps are generally more valuable when they have light and unobtrusive cancels. There can be exceptions for unusual or fancy cancels, or when a postmark is struck directly on a stamp, which collectors call “socked on the nose.”

Perforations:  A stamp’s perforations should be even, with no short or missing (referred to as “pulled”) perforations.

Gum:  Collectors prefer their mint stamps to be in post-office fresh condition, with complete, undamaged and undisturbed gum (“never hinged”).  Missing or disturbed gum – even if it’s just a small spot from being hinged in a stamp alum – can mean a steep reduction in value.  Unscrupulous sellers over the years have “regummed” many expensive stamps in an attempt to make them look never hinged.

Thin spots:  Traditionally, stamps were mounted in albums using small folded pieces of glassine paper (“stamp hinges”) that left marks on the gum of the mounted stamp.  Improperly removed hinges, or stamps that otherwise that get stuck to other paper, can develop “thin spots” where portions of the stamp tear away when a hinge or other paper is removed.  These spots are considered significant damage.

Other damage:  Stamps should not have folds, creases, holes, stains, tears, or anything else that damages the paper.  Any of these negatively affect the value of a stamp.