1960 misprint on d stamp 0

[Jay6392]

D mint stamp looks normal from afar but wen yu really look close yull see.

 

[Jay6392]

Also the date has press outline inside every number

[Coinbuf]

The mintmark just took a hit, simple post mint damage is all.  The outline of the date can be caused by strike doubling, or die deterioration, both very common and does not add any value over the face value of $.01.

[Oldhoopster]

It looks like the mm took a hit after it reached circulation.

Here are some sites that list Repunched mintmarks (RPMs).  Click on the RPM tabs to see what they actually look like

www.varietyvista.com

www.doubleddie.com

I can't tell for certain from your pics, but the extra outline is likely to be mechanical doubling (also called strike or machine doubling).  This is not true doubling and adds no additional value.  The doubleddie.com site has a tab called "Worthless Doubling" that provides an excellent explanation.

BTW: You sound like you're new to collecting.  Here is some info to help clarify things.  Coins are struck, not printed (therefore, an error is not a misprint).  Hope this helps