I am new here, so I hope this belongs here, otherwise I am sorry!
So, my grandfather just bought a 1924 Delaunay Belleville P4 (it looks like this, not his car though https://rmsothebys.com/en/auctions/al12/auction/lots/r090-1924-delaunay-belleville-torpedo) which he is planning to restore as his doesn't look nearly as good as the one in the link. But, he is having some troubles finding good information about the car's mechanical functioning. He is very aware of the fact that back then service manuals weren't as common as they are nowadays, but there is almost no documentation available whatsoever...
I did find a book that was written by the company, 'Description des chassis Delaunay Belleville 1924 : suivie d'un essai sur les différentes manières de les carrosser' which talks about the chassis of 1924 Delaunay Belleville cars, but as far as my knowledge goes, the only copy still available is being kept in the Columbia University Library (https://clio.columbia.edu/catalog/7475671) and as my grandfather lives in France, this book is unfortunately out of our reach.
So, if someone can help me (and my grandfather) with any information (detailed pictures of the chassis, engine, etc. or drawings, handbooks, manuals, etc.) it would be greatly appreciated, thanks!