Photoshop :: Filtering And Enhancement Of Old Image

I have a question that relates to a digital image that is of an old original B/W photograph.

The image is of an old, plain page of a book found by Police some 65 years ago, in it's orginal form the police had noticed what appeared to be indentations or very feint writing on this page and used graphite powder to highlight their findings and then went over the highlighted areas with what appears to be an early felt tip pen. This was then photographed and an image produced.
 
The intial image itself is quite small about 400 X 400 px.
 
It shows 5 lines of hand written characters with additional hand drawn lines.
 
Here is an example of a close up of the 'sharp end' of the two crossed lines in the centre of the page:

Here is that image reversed:

When I examined the image in more detail I noticed that the actual characters and lines were not simply black markings but in fact had various shades ranging from grey through to black within them.
 
I turned the image negative and it showed up what appeared to be smaller letters and numbers behind the initial blackened markings and lines. I have done some basic filtering and have managed to improve on the appearance but only a little.
 
The questions I have are these:
 
1. Are these real markings or are they some kind of digital noise? Most of the letters and lines on this page show signs of letters and words beneath the drawn over markings. (I have done a lot of research about micrography and such miniature writing does and did exist at the time and in fact has been around for 4000 years or more)
 
2. Is it possible for me to 'strip away' further layers of lighter coloured pixels to sharpen the markings that appear to lie beneath the overdrawn characters and lines?
 
3. This being so, what steps or processes can be used to achieve better clarity and hopefully a larger image.
 
I hope I got that right and it makes at least some sort of sense