When obtaining the Big 3, you must make sure the coins are genuine. While only a few fake 1913-S have been seen, there are plenty of fraudulent 1896-S coins (most with an added "S"). And fake 1901-S coins outnumber genuine specimens in G to VG grades!
Although the "Big 3" get most of the attention, many of the other dates in the Barber Quarter series are extremely difficult to find in higher circulated grades, including 1896-O, 1897-O, 1897-S, 1901-O, 1905-O, 1909-O, and 1914-S. As a result, putting together a complete set of Barber Quarters in higher grades is not only expensive, but takes a lot of serious searching and a great deal of luck. Perhaps only 12 to 15 original AU 1909-O quarters exist, making it quite possibly the 2nd or 3rd most difficult coin to obtain in that grade. That's rare.
For information on grading Barber Quarters, please see the Grading Barber Quarters page.
A rarity rating survey was conducted among BCCS members a number of years ago for circulated Barber Quarters. The Society
updated the survey with much more detailed information, including more specific grade ranges, additional varieties, etc.
Look at the Survey results for Barber Quarters:
Barber Quarters Census study
Barber Quarters Rarity Ratings
Barber Quarters Varieties survey
For information on authenticating the "Big 3" see also:
Authenticating the 1896-S Barber Quarter
Authenticating the 1901-S Barber Quarter
Authenticating the 1913-S Barber Quarter
Counterfeit 1901-S quarters - Thoughts and Observations
The best single reference on this series is The Complete Guide to Barber Quarters, Second Edition, by David Lawrence,
with detailed information about the series, and date-by-date analysis. This is an indispensible reference for the Barber