There were a few major mint errors, as mentioned the seated half struck on a quarter planchet, you can see the current discussion here and photos I found before the coin was "announced" in the press for the upcoming auction:
http://goccf.com/t/352929The off centered, clipped planchets are more common (but not that common) than the major errors like double strikes, capped dies and brockages. The other error you can find (sometimes unattributed) is
Retained Cuds, full
Cuds, and
DDO or
DDR, as well as quite a few RPD's and repunched mintmarks.
There are a few good books on the
Seated Liberty coinage, Larry Briggs quarter book comes to mind, as I have had a few copies I sold recently on
ebay, Kevin Flynn has some good ones as well, my favorites are any of Bill Bugert's half dollar books ( link to online versions in the link above) as well as his first book with Randy Wiley
https://nnp.wustl.edu/library/book/555396 there are quite a few books featuring
Seated dollars and varieties. Currently the only real error book I know about that is available is Sam Thurman's
Cud book vol. II available in small quantities through Sullivan Numismatics on
ebay https://www.ebay.com/itm/292777180753 if you haven't had a look at Jon Sullivan's website, I suggest that as a starting point - just for the amazing coins he always has available. Some neat stuff in current inventory.
https://sullivannumismatics.com/mint-error"Buy the Book Before You Buy the Coin" - Aaron R. Feldman - "And read it" - Me 2013!
ANA Life Member #3288 in good standing since 1981, ANS, Early American Coppers Member (EAC), Colonial Coin Collectors Club member (C4), Conder Token Collector Club member (CTCC), Civil War Token Society (CWTS) member, Liberty Seated Collectors Club (LSCC) & Numismatic Bibliomania Society member (NBS), USMex, Member in good standing, 2¢ variety collector.
See my want page:
http://goccf.com/t/140440 
Posted 09/02/2019 09:38 am
