Nickel Error?

This is a 2000 P series nickel. Nothing on the obverse of the coin seems out of the norm. The reverse of the coin however, appears to be missing its rim altogether. I'm brand new to coin / currency interest (I hesitated ... But didnt choose the word "addiction" ha....). I've educated myself a bit about coin errors/ mis strikes, and this coin's characteristics dont seem to fall under any category I've come across. My 1st guess was that this coin fell into the hands of a bored shop class student, but the precision that would require doesn't satisfy this explanation. The surface of where the rim should b is smooth on all 360 degrees of the coin.... So much so that if you look at the back of the coin from any angle, there apppears to b a dark spot / grime / shadow on the opposite angle of your vision of the coin. You have to adjust your angle to see that you arent looking at grime or a shadow or impression on the coin .....

Anyone and all input is greatly appreciated . Thanks