The thing that isn't sitting right with me: You initially made several identifications and reached out for some professional opinions. When those were met with doubt you revised half of your identifications and reversed the image to more closely match the comparisons. Correct?
Several of the hairlines and facial similarities were enhanced when you flipped the image, which I assume is why you did this....but I think the kerchief issue is a problem. I don't understand how the kerchief is shown in 'Niebuhr's' left breast pocket in your stereoview, but you somehow thought this image should be flipped, placing it on the right. Especially when the
salt print has him wearing a kerchief in his left, as is customary.
Further: if the
Henry Anthony association is being proffered as a reason this may be an earlier, 'cutting-edge' photograph, then why are neither he nor his brother in the picture? I don't think it's credible to lean on this association.
I accept that you can't be talked out of your belief that you've uncovered a historically significant find, but you need to understand the skepticism here. You've provided no 'when', 'where', 'why', or 'how' for the origin of this stereoview...only a 'who' after multiple revisions and a very subjective framing.