Notes:
In the December 1953 issue of The Numismatic Scrapbook Magazine, Walter Breen described an interesting 1797 Lettered Edge Half Cent:
"With the Frank Stewart coin collection now reposing in Congress Hall, Philadelphia, is a lettered-edge half-cent of 1797 about 1/3 of which is obliterated by being overstruck with the dies of 1796 draped bust cent S-115.  The bust and date 1796 show quite plainly, and were impressed after the half-cent dies.  The cent dies show no cracks.  It is therefore certain that February to May 1797 is the earliest period during which perfect-die S-115's could have been made.  The piece is sufficiently well-preserved to make identification absolutely certain; yet it was bought by Frank H. Stewart in 1916 as a 1796 half-cent (!) for $75 and later presented by him to the Congress Hall exhibit."

Images courtesy of Gene Braig

Significant example:
"VF-20+".  Ex - Superior Galleries "Pre-Long Beach" Elite Coin Auction, May 25-27, 2003, Lot 132, sold for $12,650.00 Ex Lester Bernstein-Stack's 4/30/86:30-Dr. Wallace Lee.  

Sources and/or recommended reading:
"American Half Cents - The 'Little Half Sisters' (Second Edition)" by Roger S. Cohen, Jr.

"Walter Breen's Complete Encyclopedia Of U.S. And Colonial Coins" by Walter Breen

"Half Cent Miscellany" by Walter Breen, The Numismatic Scrapbook Magazine, December 20, 1953, page 1170

Relevant collector organizations:
Early American Coppers Club