I can only see the things I have previously described. But then, I am restricted to using my eyeballs since I don't have any sight enhancing software on my computer and don't know of any magic incantations that might be useful. What software or incantations would you recommend?
I'm sorry, but I am not aware of what is available now. I use a "lite" version of Paint Shop Pro that I got years ago as a freebie with something computerie I bought. I think I can help otherwise, however. I've been attaching the files in .bmp format and it appears that this doesn't just expand by clicking on the image the way the .jpg images do. I'll use .jpg instead.
I've attached an image with the four plot points on the left side. I also dragged part of the plot from further north down and put it on the right side to show examples of what the normal red crosses look like. The image is only one JPEG away from the original file from Sluggo's site, which is the same as what the museum has. And I have my software set to use minimal compression in creating the .jpg files, so very little degradation occurs with each serial save.
I got a fresh copy of the map and I see what you are talking about - attached. The 4-5 west crosses are blemished vs. other crisp cross marks. Blemished, crossed out, attempt to cross out, attempt to scratch out? I'm not sure what the cause or intent would be. (Is there anything straightforward in this case?).
Note also that each of these crosses is thicker, drawn twice?, overlapped, than any of the single line red pencil crosses which are sharp and distinct along the #2 penciled flight path line(s). It makes me wonder if the west crosses are an after-thought? Why should mistakes have been only in the Portland (west) area? This could be a copy of an original map which did not have the west cross marks, like an office copy, then was worked with and crosses added by people looking at, working with, or evaluating the map (maybe in an FBI office)?
Here are sharp cross marks from the penciled flight path, for comparison.