(there was a url link here which no longer exists) - British artists suppliers, 1650-1950 - Carbon Paper Archaeology
Our friend from Belgium, Philippe Berger asked that he has a British Carbon Print from 1870s and he wants to know the list of used papers for that era.
This is extremelly wide vast array of research subject and there are very big catalogs for pointing the used paper from watermark.
If you have a very old print , hold it to the light and find the watermark and send it to British Museum , they will have an answer or directive for you.
My university library had enourmous catalogs from Holland....
For anyone wanting to access the above link at the National Portrait Gallery website......I thought at first that it was a book, then, after searching for it on Amazon, I realised that it's an on online resource; just click on the line of the letters of the alphabet for the names of suppliers under that letter ! (Think I'm having a senior-moment-day. :confused: )