I have found hundreds maybe a thousand horological books online over the last 20 years on Google books and different archives of scanned books most are far out of copyright (at least that's what they say) even Christian Huygens "Horologium" 1673 and others of similar age. I know some people have sold some of them as collections on auction sites, but there seems to be some questions of legality. I don't really agree with selling them but would a list of links to available books be ok? Or is there lists already? Not necessarily on this site I'm not sure if that violates rules for this forum? Dan.