1908-1922 6¢ Washington
(read how to identify your stamp below)
This is the 6¢ Washington. It is quite common and usually worth no more than a couple of dollars when used, however it can have reasonable value when unused. If you wish to try your luck read on...
DETERMINING THE PERFORATIONS
Count the perforations along the bottom, its as simple as that!
Below is a chart indicating the perforations of each Stamps Catalog #.
DETERMINING THE WATERMARK
To know which watermark a stamp has, one needs watermark fluid or lighter fluid (both of these are extremely flammable and should be used with extreme caution, outside, in a safe area far away from combustible materials). Soak the stamp in the fluid in small plate with a black or very dark color. The watermark will show, sometimes faintly by looking at the back of the stamp. The watermark fluid will quickly evaporate from the stamp, leaving the stamp and its gum intact.
There are two types of watermark you will come across. These are;
The watermark will have part or all of the letters U, S or P, as shown above. The upper USP letters are made of double lines, this is known as watermark 191. The lower UPS is made of single lined letters, this is known as watermark 190. There are several varities that have no watermark. Below is a chart indicating the type of watermakring that can be found on each stamp.
DETERMINING THE PAPER
Identifying the type of paper the stamp was printed on is not easy. Usually one does not need to bother with this as over 99% of the 6¢ are printed on regular paper and their price is un-affected by the type of paper. There are two types of papers that the Post Office experimented with in an attempt to save on costs. These are all rare, they are;
China Clay Paper
However, having said all this, certificates are issued for these (on what basis I have no idea), and they do sell at a premium. According to Scotts the paper was accidentally given a high mineral content (its aluminum) and the paper is thick, hard and grayish, often darker than "bluish" paper. The differences are, shall we say, subtle. My advise is not to buy even a certificated version, as Scotts has little supporting evidence to have awarded this category of paper catalog status.