I'm beginning to wonder if this forum is about classic and vintage bicycles, or about classic and vintage bicyclists.

Along those lines, I have a t-shirt with this design printed on it:

http://www.bbhq.com/gr10b/45adapter.jpg

Everyone over the age of 45 knows what it is, and a surprising number of people younger than 25 know what it is, but almost no one between the ages of 25 and 45 has the slightest clue what it is.