1972 D cent with blank spots on reverse?

Found this while roll hunting. I originally set it aside for it's great condition, but then later noticed the blank spots on the reverse, especially the missing "E" in E Pluribus Unum. Worth anything, or just wear?

 

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grease filled die (assuming steps and top of monument are lower than rest of the coin)?
How do the missing areas look under a 10x loupe (or even higher power microscope)? Any indication of friction/scratching/rubbing/etc.?

 

No signs of running or scratching. Just smoothed out blank areas.

 

Looks like a greaser.

 

I would almost say a worn DIE. I know I have seemed a similar effect on some 1980's cents

 

if worn, I would expect it to be more uniform. The UNITED, AMERICA and ONE CENT appear to be bold.

 

That area below the memorial is supposed to be blank.