Reading the board
Each card shows the largest print the Met's file makes at 300 dpi without cropping — that's the sharpness you'd want for something you'll stand close to. The biggest file in this set isDiscomedusae (Kunstformen der Natur), at 2,300 × 3,300 pixels: enough for a 7.7 × 11 in print at 300 dpi, or 15.3 × 22 in at poster sharpness.
Every page has a size chart against standard frames, the museum record, and the frame and light that make a print look like it cost more than it did. The file itself is free. It always was.