I know the guy behind this, David Lowe. He's been working on it for a long time. It represents a massive amount of research and work and will be useful to many people.
Congratulations to David, the team, and the NYPL!
Thanks, Ratsbane! I'm David Lowe the editor of the data in PIC (the beautiful interface was built by the NYPL Labs team, specifically Mauricio Giraldo). Happy to field any questions or comments.