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 isAn Experiment on a Bird in the Air Pump, at 5,639 × 4,226 pixels: enough for a 18.8 × 14.1 in print at 300 dpi, or 37.6 × 28.2 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.