I noticed that the letters and numbers sometimes look different is this right or is it because of wear to the die
It's only by great coincidence that any two coins (outside related issues like Seated stuff, etc.) use the same fonts. They're generally designed by different persons, and intended to be unique unto themselves.
I think you're right! The first one that comes to mind for me is the 2008-W SAE and the 2008-W SAE, REV of 07. Chris
OK, looked at that way.... There may be *minor* year-to-year changes in conjunction with a broader design revamp. More importantly, keep in mind the lettering on a coin is not vertically-sided. It tapers as the void in the die gets deeper, and on the coin the tops of the letters are therefore more narrow than the bases. So, as the coin wears, the lettering will appear to get "bolder." Letters will appear to be closer together, and the stroke will increase in width.
Is there different letter fonts for coins ? Simple answer, yes. Think of the Ike series for one good example.