Updated July 25th, 2019.
The original Macintosh team’s signatures are engraved in the plastic of the original Macintosh’s case. The idea (according to Steve Jobs) was that since the original Macintosh was art and artists sign their work, the original Macintosh team should sign theirs. So they did. The signatures are inside the case, seen by very few people… but they are there. I have a Mac Plus, which was the third iteration of the original Mac, and the signatures are present there too. I should take a picture.
Meanwhile, here’s a picture from Folklore.org.
You can read all about it at Foklore.org. Warning: you can lose an entire morning on that site. It’s that much fun.