I have come across a Google Books footnote reference in a Polish book called Legiony Polskie, 1794-1807 by Jan Pachoński. It refers to an Archive called AE, followed by things like AE, Memoires/Pologne/Toscane etc. Then comes rkps (Polish for manuscript) number, then s. (strona - Polish for page) number. There are also some archives listed as AS with Italian cities, which I take to be Italian 'Archivo di Stado', which are Italian state archives.
Does anyone have Panchonski's books? Or any ideas about the AE ref, given the manscript/page numbers? I am thinking it is a French archive.
Thanks for that confirmation, Ian,