Posters have been used almost as long as people have been roaming the earth. All in some way are historical as they depict some event, person, scene, etc... Posters were originally used to advertise public events and even new laws. Posters can be an art form as well as many have pictures on them to include original art or reproductions of classic art.
For instance, for many years Georgia O'Keeffe supported the Santa Fe Chamber Music Festival by allowing the Festival to use her work to advertise the event. Most of these posters no longer exist. The few that do can be quite valuable. Figuring this out is the trick!
Like with any piece, condition is everything. Most posters I have looked at for potential purchase have some damage. Many times it is water. The stains are usually obvious. Those wavy brown lines tend to stand out. But sometimes it is more subtle. A slight wash-out can be a clue. Maybe the paper is buckled in the area where the poster got damaged. Any non-conformity to the normal smoothness of the poster bears a closer examination.
Tears are a common problem. Most posters are not made of the highest quality because they are only made for a certain event, or maybe they are an old pin-up. Either way, the quality of the paper or poster board is only.
Folds are another problem Never fold a poster! Roll them up and store or ship them in a tube. Folds not only ruin the appearance of a poster, many tears occur along them.
Bends and wrinkles happen when posters are handled improperly. Handle posters with care to avoid these.
Edges and corners should be sharp and clean.
Fading is also a problem and is caused by exposure to a lot of sun or sharp light. Keep them away from direct sunlight when displaying.
All of the mentioned problems devalue a poster, sometimes to the point of making them worthless.
