May I ask for some expertise with possible photo examples. I'm looking for a explanation and a visual example between an 1840 Seated Liberty half Small Letters and Large or Medium Letters varieties. Then add Reverse of 1838 and Reverse of 1839 to the mix. I'm looking at my Red Book, but I still don't get it. Thanks.
Your best choice is to go right to the source. This guy wrote the encyclopedia on Seated halves, and has generously made most of his work available online for free: http://www.lsccweb.org/BillBugertBooks/BillBugertBooks.php If you post pictures of the coin you are trying to identify, we can help.
@physics-fan3.14 I hope you don't mind that I passed on your reference re Seated halves to @Courtney Plum.
Well, I have no idea who that is. But it isn't my reference - it's Bill Bugert's. He's made it available for free on the internet for the specific purpose of sharing.
A new member. If you click on her profile and look at the post it's about some CC Mint Liberty Seated Halves she bought.
Small letters, introduced on the seated half in 1839. The letters are very small and WELL away from the rim. Medium letters this is actually a leftover 1839 O capped bust half rev die. Letters are noticeably larger and close to the rim. Note the space separation between S OF A . Large letters this rev started in 1842, the letters are slightly larger and still close to the rim, but now S OF A are so close together it almost looks like one word. The left foot of A is under the upper serif of the F. Calling one of them rev of 38 is a bit confusing because both the small letter and medium letter reverse were 1839 reverses, but the medium letter is the same style that was used in 1838.