I found this image while surfing around this morning. Don’t know about authenticity, but supposedly, these are the business cards of Josef Müller-Brockmann, Paul Rand, Adrian Frutiger and Helmut Schmid. I’ve seen the Paul Rand card before, so that one could be legit. Either way, these are lovely. The Frutiger card is definitely the least functional.
Update: Michael Bierut confirmed on Twitter that the Rand and Müller-Brockmann are the real deal.