Here's an interesting article on the Nobel organization's official website. This may add fuel to the cast versus struck question. I do not believe it is written by a numismatist. No doubt the three "temporary" base metal medals of 1901 would fetch as much or more as the gold ones at auction today, don't you think?

According to the Statutes of the Nobel Foundation, given by the King in Council on June 29, 1900, "the prize-awarding bodies shall present to each prize-winner an assignment for the amount of the prize, a diploma, and a gold medal bearing the image of the testator and an appropriate inscription." The medals for Physics, Chemistry, Physiology or Medicine and Literature were modeled by the Swedish sculptor and engraver Erik Lindberg and the Peace medal by the Norwegian sculptor Gustav Vigeland. The medal for The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel (established in 1968 in connection with the 300th anniversary of the Sveriges Riksbank), was designed by Gunvor Svensson-Lundqvist.