Design A45A 2c Jackson - A Particular Mark Under The Left Scroll!!!

One of the things I learned here, on SCF, is that the most constant element in identifying a stamp is the design. Anything else is subsequent to the printing of the design: paper, perforations, size etc. Studying and analyzing various large bank note stamps, I believe I found a particular mark, which along the years was ignored, most likely assumed to be caused by excess ink.
Below is a magnified image of this particular mark at the top of the first line under the left scroll on a 2c Jackson:



And here is the same area of a Scott#157 sold by Robert Siegel in 2014, with no trace of the above mark:





Before answering to this post, please check if any of your other A45 and A45a present such a line: it ends obliquely to the right, towards the point of junction of the scroll lines! Then, please look through the available higher definition images of Siegel Census and Arago, with focus on the issues printed from 1879 onwards.

Finally, please answer this question:
can this be a mark resulting from burnishing the plates used by American starting 1879 for producing again this design?
If your answer is 'yes' then please consider the following!

Some of the certified Special Printings have this particular detail, to a greater or smaller degree: at least three specimens are showing it clearly.
If this is a particularity of latest issues of 2c Jackson (after 1879) then how were the certified Special Printings assessed, please? Would this be a design detail able to qualify or disqualify the existing and future certifications?

Which line? You know where you want us to look, but from your description I can't tell. An arrow pointing to the spot would help. Or a circle around the area. So would a comparative image that does NOT show the feature in question.

Essayk, done! You're absolutely right - my fault, sorry

Thank you. What is it about this mark you want us to notice? Guide me to the point you want to make.

I still don't see it... could you make a side to side comparison with one not having this mark?

Also I am not sure about your propositions: Do you postulate that:
- the mark is to exist on A45 and A45a design (as part of the known "secret mark") or only one of them, and which, and why?
- the mark is existing on special printing and on the normal issue, or on one of them, and which, and why?

To me, it looks like some of the Special Printings of 1880 the stamps were presenting this particular mark, while none of the previous issues seem to have it. So far, I don't possess any certified A45 or A45a stamps. That is the main reason why I am asking for your help, here, in the forum.

Don, you will need a very large supply of popcorn on this one

but you said that the particular mark would have been there since 1879?
(edit: ok I think you said that it was added in 1880...and after that it was again deleted?)

I will look at some of my 2c stamps as I obviously also love detective work :), but I am still not sure about what the working hypothesis is.

What did the designers intend? How can you check that out?
Hint: you're going to need access to some die proofs.

I will help you with that. If you search on this forum for "2c secret mark" you will get a host of thread options. Try this one: https://goscf.com/t/46707&SearchTer...,secret,mark

and scroll down a ways. Why must you start with the die proofs?

Interestingly, on the swedishtiger.com, only 2c Jackson (#193) shows just what you are pointing out. https://www.theswedishtiger.com/x1880.htm
The dark line is even more pronounced on the link. None of the the other A45 and A45a designs, including vermillion color, on theswedishtiger show it. It may not be definitive since these are only a small number of examples. It seems to me that on your example above and on the website that there are a few horizontal dark line extensions in the vertical shading as well. These horizontal lines are to the left of the scroll. Bring on some more popcorn.

Essayk, even if it was not an intentional design trait and it was the result of natural wearing of the plate, it still can help identifying stamps from a certain moment onwards.

Stamperix, my hypothesis is that sometime between the end of 1879 2c Jackson series and the beginning of the 1880 Special Printings the 2c Jackson plate started presenting this particular mark (on purpose or by accident, at this point is not really relevant). If the hypothesis is correct, then it will ease the identification of the Special Printings.

Quigngt, thank you for pointing it out!
So far, I went only through Arago and Siegel images

Image resolution in Siegel images is too low to tell anything about it. I downloaded one example which is 670x800 pixels, here you can't say anything about such a detail. Also, in your image you have really a lot JPG artefacts, also difficult to tell anything. To maintain our popcorn guests I suppose you upload the small part of the design of your original high resolution scan, without any editing, and with only few JPG compression. Look how good essayk's images are here: https://goscf.com/t/46707#445707

Try Siegel Census images. Some of them are of a high enough definition.
The images that I upload are not subject to any filtering or retouching unless I want to point out something in particular - ie on one of Don's recent posts about a cover, I did use Gaussian filtering.