The sharpness is not perfect in the photo... There appears to be a red fiber in the paper. The blue/black one at the edge is not a fiber in the paper but a mark of some kind on the paper.
If this were on silk paper, I would expect to see multiple threads and I am not seeing them in this example. I don't think it is the resolution, I just don't think this is an example of silk paper.
"If this were on silk paper, I would expect to see multiple threads and I am not seeing them in this example."
Au contraire. The 1st issue silk papers are a completely different animal from the silk paper used in the 2nd and 3rd issue revenues. You frequently see examples with only a single thread. In fact, for some stamps the blue silk threads are so sparsely and/or unevenly mixed that only one stamp in a multiple will exhibit the telltale threads.
That is why you often see stamps with the right paper characteristics to be a silk paper but cannot be proven so due to the lack of silk threads.
Also, it is not JUST the presence or absence of silk threads, but also the right paper color and consistency. An image of the front of the stamp would be needed as well.
See my reference page on 1st issue silk papers here:
Oh, I agree. My points were that (1) frequency of blue threads is not a good indicator; all it takes is one thread in the presence of other positive indicators, and (2) an image of the front would be required to make a final assessment.
USRevenues, Your site is now bookmarked and I will be studying it to learn more about this area of the hobby. I have developed a big interest in US Revenue Stamps and have collected a large number already.
on deeper examination of the above stamp I am quite sure it is not silk paper as the paper doesn't have the right texture in comparison to the examples on your site.