Images courtesy of R.M. Smythe

Notes:
The following is reprinted (with permission) from "The Complete Guide To Certified Barber Coinage" by David & John Feigenbaum:

"The Barber quarter series consists of 74 regular issues, with no significant varieties. While it does not have a rarity equivalent to the 1894-S dime, it is a very challenging set with three well-established keys: 1896-S, 1901-S and 1913-S. Their very low mintages; and scarcity even in the lowest circulated grades, distinguish these three. In fact, the 1913-S quarter with a mintage of 40,000 has the distinction of being the lowest mintage (regular issue) silver coin of the 20th century.

A total of 15,315 Barber quarters have been certified by PCGS & NGC in mint state [As of 1999] . This is very close to the 16,918 mint state Barber dimes certified. Yet, the 264 million Barber quarters produced is about half of the 504 million dimes made. Of the 74 dates, just three are R6 in total mint state. Seven are R5 [Rare], 12 are R4 [Very Scarce], 15 are R3 [Scarce], 15 are R2 [Common] and 22 are R1 [Very Common].

There were 10,735 mint state Barber quarters certified in March '94, when the second edition of The Complete Guide To Barber Quarters was published. This means approximately 1,000 mint state quarters have been added to the population reports each year since then.

Because there are more collectors of Barber quarters in mint state than Barber dimes, any dates which are R4 or higher enjoy a demand greater than their availability, especially in MS 63 and below. Lately, this has been true of the very high grades also.

The working hub (design) used in 1892 was modified during that first year to accommodate better stacking of the coins in a roll. Therefore, we have a type I and type II reverse for 1892 and type II from 1892-1900. In 1900, the hub was again modified slightly. These changes can all be distinguished by the relationship of the eagle’s left wing. (See illustrations at left.)

With patience a nice mint state set of Barber quarters can be assembled, but it will take time."

Sources and/or recommended reading:
"The Complete Guide To Certified Barber Coinage" by David & John Feigenbaum