On a recent visit with a friend and her newborn daughter, I was completely taken with an enormous scientific diagram of a snail hanging by the crib, aglow with the thrill of science and the unmistakable vibrancy of mid-century graphic design. I asked about it — she said it was a vintage French classroom poster she had acquired at the Oakland Flea Market. Determined to find out more about its creator, I had only the tiny inscription in the bottom…