US Scott 443 Washington 1c Line Single?

Although it's safe and time tested. I've always had the heebie-geebies about dousing my stamps in a flammable fluid (or fuel)... I have used it and never had a problem but eventually I managed to get a inst-a-tector then a signoscope for water mark identification. I do still use the lighter fluid from time to time though.

Neither is as effective as Clarity watermark fluid, available from the American Philatelic Society or Subway Stamp Company in Altoona, PA. The most effective means of finding watermarks may be a Video Spectral Comparator. The Smithsonian National Philatelic Museum has a VSC6000 in Washington, DC.

Also read the fine print on the Ronsonol container. It is made by Zippo Manufacturing Company in Bradford, PA. A couple of stamp dealers have said that lighter fluid should be tested each time a new container is opened, especially if packaged outside of the United States.

cfrphoto - I don't know about some foreign stamps but US stamps don't require spectral analysis to ID a watermark. At least not in my experience. Lighter fluid, an Inst-a-tector or on the high end, a signoscope has been sufficient. Do you know of any examples of a US (or foreign) stamp issue that these won't detect?

Some perf 10 and unwatermarked coils are very difficult. The worst offender is the 2¢ type II Scott 491, which is a truly scarce stamp. Now that advanced forensic equipment exists in parts of the expertizing community, I am confident that some stamps thought to be unwatermarked will be found to have watermarks. The highest profile case is 476A, the orange 30¢ perf 10 stamp. While many believe that the unwatermarked variety exists, others claim that all of the stamps in the two complete sheets and a partial sheet are actually watermarked. It would be possible to determine if watermarks exist or not because the position of each stamp in the sheets found was recorded. This means that a stamp believed to be watermarked can be used to determine the position of the watermark on other stamps in the sheet. Until a "U" or a "P" is found in a position matching a predicted position, it will not be possible to convince those who believe that "watermarks" found on some 476A examples are not from partial letter "S" impressions left because the raised watermark letters were not completely removed from the dandy roll when watermarks were discontinued. Partial "S" examples are relatively common in early unwatermarked examples. For years, it was believed that the type II vertical coil (Scott 487) also existed in a watermarked version. No examples with a clear watermark have been found.

The worst stamps most likely to be misidentified watermarked examples include the 491 horizontal coil, 476A, 477 the 50¢ perf 10 unwatermarked sheet stamp and some of the other perf 10 stamps like the 6¢ or 8¢. It is exceedingly difficult to see a watermark on a yellow or orange stamp using lighter fluid, unless the correct color filter is available also. With Clarity, violet or purple stamps are difficult without a color filter. In some cases, like the 50¢ 477 or 491, access to a color reference will help weed out watermarked stamps with unclear or partial watermarks barely grazing the stamp design.

The bottom line is that many perf 10 stamps in the marketplace offered as unwatermarked are misidentified.

And if you can't ID the watermark of the absence of it, always presume it's the cheapest stamp.... how many posts we see with peoples always jumping to the most expensive one..

cfrphoto, good info thank you. I'll have to re-examine a few of those issues and take a deeper look. I work down the street from the Postal Museum in DC and find myself in there a couple times a month. I talk to the staff from time to time, maybe I'll see if they can confirm some of my findings.

area66, you are 100% correct.