drawing on laid paper 1700 or older help with secret mark

purchased at san Francisco flea market. when i got home and took out of frame to see it was a print but to my surprise it was real and on laid paper. for some reason the frame doesnt look old but the glass was hand blown , called a pane or panel sheet of glass.
two edges are straght and two are hand cut with pliers. also one side of glass has waves all thru. this glass was used until the 1700's. i also research the laid paper and its also 1700 or earlier. the drawing looks done by a master but there are two parts that look like a child did it and i dont know why. the shadow next to nose looks overdone and two line on both sides of face look too thick , not matching the others, . there is a dark small spot bottom left of chin, when put to sun light it turns luminous yellow, and when uv light aplied it disapears. i did manage to take a picture of a mark that looks like the letter "R".
please give me your opinion, junk or treasure?

 

I think the paper is machine made.

Machine made papers can be patterned to look like laid.
This is a paper made in 1874:


This paper is c1600:


On the first example, note how evenly the light is transmitted through the paper. On the second example. the paper is darker at the chains, lighter halfway between them. This is because when the paper was made by hand, the pulp tended to accumulate more heavily at the chains, but with machine made paper, the lines are mold impressed.

The two spots you see on the older paper are called "Vat Man's Tears". They are from drops of water that hit the paper as it was removed from the vat but still essentially in a pulp state.

 

Found this interesting..

 

When I was doing my research, i read a part where the lines that are wider spread, those lines in laid FROM 1700 and before had a shadow or darker appearance because of some chain that created suction during the process. There is a picture that was not blown up that shows that in mine.
You have to click on the small image under the first 10.

 

It's a drawing? Done with what?

Debora

 

Hand made paper= Laid paper

 

"Laid paper is a type of paper having a ribbed texture imparted by the manufacturing process."

Debora

 

https://en.m.wikipedia.org/wiki/Laid_paper
Here is a link to what I'm talking about.
IT CALLED ANTIQUE LAID PAPER.