Here is a little primer to familiarize yourself at what your looking for while doing watermarks- Note that they can be in reverse or upside-down or both. Sometimes only a tiny piece of a letter is only visible. These can be troublesome but therein lies the challenge! Single line watermarks: Double line watermarks:
The single line can be very tricky on single stamps, the bottom right in your block is a good example (with virtually no watermark).
I totally agree however, they (the single line watermark) are probably the easiest to spot of the two than the double line watermark assuming there is enough of it on your stamp!
Here are some very helpful links for the identification of the United States Washington/Franklin series. http://www.1847usa.com/washfrankmain.htm http://www.askphil.org/W-F/Index.htm
This is a post from another forum that explains a very useful watermark detecting method, albeit a difficult one at first but after a time or two it gets second nature. PostmasterGS is the creator of the technique. I had to give credit where credit is due. Now go try it out!
