Over at the World Famous Design Junkies blog, I like their photos of vintage sewn-in clothing tags.
As a fan of vintage clothing, the first thing that I do when I find a piece that I like, is check the tag to see the size.
If a manufacturer name on the tag is no longer around or changed names, that gives you a big clue of the age of the garment. Letter fonts are fun to look at, and there's another clue to solve the age mystery. Fonts are popular one year and discontinued the next.
Vintage clothing tags can tell you so much about the era of a garment, plus it's just plain fun to see graphics from the past!