I have not been presented with any evidence that would cause me to change my mind.
Further, we felt that these essays probably dated from the early 1880s due to the currency change in 1880.
A reader of this blog, Dr. Wilhelm R. Guggisberg, recently sent me some scans of these essays showing a watermark that I suspect is a papermaker’s watermark. It has the numerals “8 0” and I suspect it is part of a year date of “1880.”
I am including the scans sent to me and I hope other readers will check their holdings of this essay to see if they have any material that would confirm or refute the “1880” date.

(Pair showing two different designs)


I am not sure how well the figures “8 0” will show up but can attest that they are there.