Whaling logbooks sometimes had stamps of whales in them. There was a blank space left in the center of the whale and inside that space they recorded the number of barrels of oil that were taken from the whale. I think that different types of whales had different stamps. Stonington's log book has some whale stamps inside. You can see which pages they are on by viewing the transcription.
Now I'm homesick for Mystic Seaport - a place I've only been to once.