The LM stands for Logan/McCloskey (Russell J. Logan & John W. McCloskey), authors of the book Federal Half Dimes/1792-1837. The LM varieties are to these half dimes as VAM is to Morgan and Peace dollars.
The good news is this book isn't terribly expensive and is fairly available (unlike some numismatic books, notably the capped bust dime book). Buying the book is highly recommended. BTW... if anyone is interested, I can direct you to a copy of of the JR capped bust dime book. There are 5; three are spoken for (sold in minutes). I don't know how long the other 2 will last so move quickly.
Regarding the coin on this thread - nice strike from an early die state. Dipped at some time; a coin with such little wear should show much luster. Not a bad coin. Dunno the die marriage; I don't have my book handy.
I believe it's an LM4. If you look at the address of the images as they are listed on the PCGS BST it will tell you the source and the source in this case has the LM number listed in the name of the coin.
What do you consider not terribly expensive and fairly available? It has been out of print for awhile not and it isn't really easy to find. Last I knew it was starting to push the hundred dollar mark. (I'm not in the market for one, already have a copy. I agree about the dime book though, TOUGH. I got lucky though, last October a dealer at the Kentucky State show had just bought a collectors library (some good stuff in it too.) and he had a copy, unused. Picked it up for $20.
