Perhaps when you were in elementary school you learned a pangram or two. A pangram (from the Greek pan gramma) is a sentence or phrase that contains all the letters of the alphabet. Here is one that you may have seen:
Pack my box with five dozen liquor jugs.
Cases for loose type (also called job cases, or California job cases) are often labeled with a strip of paper on which a pangram has been printed in the font the case contains, to help you envision what your printed material will look like.
Over at Green Chair Press, Susan has a wonderful post today featuring some great photos of job cases adorned with such pangrammic magic. My favorite:
For more printerly/book bindingly/artistic/poetic wonder, visit the blog for yourself.