1965 Philadelphia Jefferson Nickel Doubled Die Obverse .

i have a question mr COOP ? I see some separation on some letters ... is that part of the deterioration of the coin too ^?

No, your coin shows MD and die wear.

Centavo69, I think you probably understand that everything on a die comes out opposite on a coin. Everything raised on a die comes out recessed on a coin. Everything recessed on a die comes out raised on a coin. I think you understand all that, it's pretty basic.
If you take that one step farther, you will realize wear on a die adds recess to a die. The wear recess on a die becomes raised on a coin. It's often mistakenly thought to be doubling. There are several ways to tell "die wear doubling" from a Doubled Die. The "die wear doubling" on a coin is usually sloppier and raised very little when compared to the Doubled Die.
Machine Doubling (MD) AKA Strike Doubling, is also often mistaken to be a Doubled Die. It is caused by unintentional extra movement of the die at the time of the strike. The die first strikes the coin leaving perfect devices, then unintentionally moves and alters the devices. Depending on the direction of the unintentional movement the altered devices can be smashed flat at their edges (usually with striation lines) or the devices can come out with as little as lines in them from just a "kiss movement". This phony "doubling" can be differentiated from the Doubled Die by being not as tall and by being part of the original device. The Doubled Die is not part of the original device, it is alongside it. Understand that, and you will understand Reduced Devices. Take the time to understand these three paragraphs, I think they should help you tremendously.