[The following excerpt is published courtesy of DLRC Press and its author, David Lawrence This information was originally published in 1991 in The Complete Guide to Barber Halves
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MAJOR DESIGN CHANGES
HUB CHANGES:
A new obverse hub was introduced in 1901. Coins of both hubs can be found in 1901-0 and S. Proofs of 1901 are from the Type I hub, while business strikes seem to be of Type II. The difference is most readily detected at Liberty’s ear. In the Type II hub the ear has a fuller lobe and a clearly cleaned rib of central cartilage (Lange). Breen reports minor hub changes in 1908 and 1912, but I have been unable to discern the differences he describes.
Obverse 1900 Type I Hub / Close-up of Liberty’s Ear Type I Hub
Obverse 1902 Type II Hub / Close-up of Liberty’s Ear Type II Hub
MINT MARK CHANGES:
New Orleans: Most New Orleans Barber Halves have a medium sized “O” Some of the later years (1903 & 1905) seem to also have a more wide open “O” It may turn out to exist on other years as well. A micro-O mint mark— the size of the “O” used on the Barber Quarter —can be found on some halves in 1892. Beistle also reported it for the 1898-O These coins are rare.
Regular ‘O’ / Wide Open ‘O’
San Francisco: At least four types of “S” mint marks can be identified in the series. Early dates, 1892 -1898 have a well rounded, closed mint mark (Type A). The Type B, found also on 1898 halves, is more open. The third “S” (Type C) is straighter and can be found at least as early as 1899. It seems to be the predominant shape until late in the series when a very thin “S” appears (Type D). Some years have several mint mark shapes and some mint marks do not exactly fit the description of any of these four types. This is an area which could use further study.
‘S’ Mint Mark-Type A / ‘S’ Mint Mark-Type B
‘S’ Mint Mark-Type C / ‘S’ Mint Mark-Type D