1793, 1794 or 1873 (including all the open and closed varieties) Harry X Boosel (AKA Mr. 1873) made the 1873 research famous with his book 1873 - 1873. I'm still looking for a copy and have it listed in my wants page here at CCF, I do have a photocopy of it though, and there are so many 1873 varieties it makes my head spin!
"westcoin wants" - Numismatic Books & US
Two Cent Pieces:
https://goccf.com/t/140440
"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