A little rolled thick planchet http://www.error-ref.com/rolled-thick-planchets/ Here is a quarter I own on a rolled thick planchet
Definitely out of tolerance, by about .2 grams, might be worth a small premium. If you are thinking about slabbing it don't unless you just want it in a slab because it will cost a LOT more than the coin is worth.
The heavier one is a 1982 and the lighter one that you are comparing the weight with is a 2007. Did they change the metal content or materials used between the two years? That's what I would be thinking. Do you have a different 1982 that you can compare the weight with? I'd want to compare the weight with the same year of nickel. Just like quarters. For example, look at post-silver 1960's quarters compared to the newer quarters. Washington looks like he's not missed any meals on the more senior quarters. On the new ones it looks like he's anorexic.