How to find the value of a stamp
There are quite a few contributing factors in determining the value of a stamp and the first one is age. You can usually determine the age of a stamp by the type of picture and the grade of paper used, if you are having difficulty then take a photo and ask for help on a stamp collectors forum such as http://www.stamp-forum.com/
Where was the stamp produced? The political or social history of that country may have an impact on the stamps value, particularly if it is a commemorative stamp.
Is the design positioned directly in the centre or is it offset, both perfect and flawed specimens can hold their own unique values.
Has the stamp been cancelled? Heavy cancellation marks which affect the design can diminish a stamps monetary value dramatically.
How many copies of the stamp were originally produced and how many are left now? Rare stamps are typically more valuable than stamps which were mass produced.
There are three different grades which can be used to evaluate a stamps condition and they are: sound, faulty or defective. A sound stamp has no imperfections, a faulty stamp can have a few minor imperfections and a defective stamp has major imperfections such as creases, tears or stains.
If all of the above methods appear to be inconclusive, you can consult a reference book or even search online for the value of your stamp. Auction sites such as ebay may have similar stamps for sale or for very rare stamps you may need to visit a professional stamp collecting website.
If you are serious about getting an accurate valuation of your stamp for insurance or re-sale purposes then you may need to visit a stamp show or to pay for a professional stamp appraisal.