Letters In A $10 Serial Number?

It's the series numbers, started since the big-head versions

A is 1996 Series, B+W (although it was the only one, it's better to start listing now for future purposes)
B is 1999 Series, B+W
C is 2001 Series, B+W
D is 2003 Series, B+W
E is 2004 Series, Colored 20 and 50 only
F is 2003A Series, B+W
G is 2004A Series, Colored 20 and 10 and 50
H is 2006 Series, B+W 100 only
I is 2006 Series, Colored 5 10 20 50
J would be Obama's series, B+W 100 if the nextgen isn't issued yet
K would be Obama's series, colors

So basically the first letter means the series. This makes the notes easier to track, so instead of having to track both the number and the year, now it's just another prefix on the serial.

As for the star note... well it's just a star note... with the new type serial numbers

hope this helps

*And by Obama's series, I mean the new signature and series when Obama starts appointing the new Cabinet

Beginning with Series 1996 Federal Reserve notes, there are two prefix letters to the serial number. The first prefix letter indicates the series year. The second prefix letter indicates the issuing Reserve Bank

Dillon,

This dual serial only started in 1996. Before, if you had it ripped in half, all you can do is make a guess to who was on the other side of the signature.

This only works with the big head notes, with serial XX12345678X