I added a bunch of plate number and other info on this page to help in dating Breitkopf & Hartel publications. I'll add additional info as I come across it and urge everyone else to do the same.
Ultimately I would like to see this type of detailed information available for all publishers. Some, like Peters, are notoriously difficult to date due to their nasty habit of sticking bogus copyright notices ranging from the 1930s through the 1960s upon works originally published as far back as the 1880s. Other German publishers indulged in this practice, too, but Peters was about the worst.
Breitkopf page
Moderator: kcleung