One of the most consistent appeals to tradition is women wearing veils. (I have written more about it here, here and here.) For the record, I love to see women wearing veils and hats at Mass, but as a general notion, nothing says tradition as much as the veil.
But how traditional is it? I have been collecting photographs from Catholic tradition and was surprised to see that in photos prior to 1960 most of the women were not wearing veils. It seems that the period during which veils were worn was short—not more than ten years (early to late 1960s). Rather, women wore hats. Most but not all the photos were taken in the United States, but they consistently show women in hats, not veils prior to 1960.
Do we need to adjust our notion of what type of headwear is traditional for women? I love veils and think that most women today are more likely to wear a veil than a hat. Veils also link more closely to the biblical tradition. However, the photograph evidence is clear that hats predominated prior to about 1960.
The photograph above was taken in my parish in 1954; it shows hats, no veils. The video below contains photos from various places in the U.S. and Europe as well as various times, nearly all from the early 1900s to the late 1960s. I provide some commentary as well. (The video is quite lengthy (more than 12 minutes long), so I have put the pictures into a pdf document and posted it here: Find the Missing Veil.)