So the little pictures at the bottom, are they different types of exposures? If so, too bad they dont have one that says MeowtheKitty. I could make all the items in your photos look like they are orange with white stripes.
Marites The letter D that you are asking about is the mint mark for Denver. I now understand your question . Yes the D isn't extra...letter.
I can see what you are asking about and looks to be a small F or part of a E but not sure what it could be. I thought that it might have been sunken in. Sometimes a coin die can become clogged and the debris can fall out of one or more letters from the clogged die and get pressed into the the coin when the die strikes it. We call this dropped letter coins and some people including me collect them. It would be really unusual for a extra letter to get pressed into a coin die to make a extra raised letter unless from something like clashed dies. In this case I don't see evidence of a die clash. Maybe something hit the coin just right to gouge into it and force the metal in this area to raise up.You may want to let someone that knows about coins take a look at it.
Thanks for the new picture, but it has too much glare for me to tell anything about it. If you can, post a picture like this without the glare:
If you mean that tiny little raised piece of metal that's look like an R has a flat spot than a longer tail which goes to and rides the rim I think it's a die crack.