This is the 15¢ Washington. It is quite common and usually worth no more than a few dollars when used, however it can have reasonable value when unused. As there are only vour variations of this stamp, identification is relatively easy.

There are three variations of this stamp. They are catalog numbers 340, 366 and 382. Catalog number 366 is so rare that you do not need to bother with it. That leaves catalog numbers 340 and 382. The difference between the two is in their watermark. See below.

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;

Watermark 191

Watermark 190

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. Below is a chart indicating the type of watermakring that can be found on each stamp.

	Type of Watermark
Scotts #	Double Lined(191)	Single Lined (190)
340	X	-
366	X	-
382	-	X

China Clay Paper
I challenge most experts to identify this paper. My own opinion is that it should not be listed in Scotts catalog due to the difficulty in its authentication. China clay paper is called an 'experimental' paper. There is no clay in the paper and in fact there is very little to distinguish this paper from normal paper. At there time of printing there was a flood and this caused the water to wash the paper to be dirty, so miscroscopic examination of the paper might reveal particles of dirt in the paper fibers. The flood was short lived, shorter than the printing of this paper, so not all the supposed China Clay papers have this characteristic. To read the stamps history and an independent opinion click here. To see images of the stamps click here.

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.

Bluish Paper
If one reads Scotts one is led to believe that the paper used for the 'bluish' paper stamps was comprised of 35% rag stock. Which would lead one to believe that this aids identification. Unfortunately only 10% rag stock was used, making the difference between normal paper and bluish paper subtle. To show you how subtle, look at the stamp on the left, it is made of bluish paper. You can see the paper is just slightly darker. It does, in fact, have a slight greyish-blue tint to it. A bluish paper stamp will require certification. The 5¢ blue paper is exceedingly rare and it is difficult to identify because the blue of the printing frequently is echoed onto the paper (see example at the top of this page)

Bluish Paper

Normal Paper