 Many stamps are rarer, and consequently much more expensive, in unused condition, such as the Penny Black, which in 1999, catalogued for $1,900 mint and $110 used.The reverse is true for some stamps, such as the hyperinflation stamps of Germany, which may be worth many times more if genuinely postally used.Where stamps are much more valuable in used condition than unused, it may be advisable to have such stamps expertised to confirm that the cancellation is genuine and contemporary.