It doesn't look mis-shappen at all, so it's probably not a wrong planchet strike, unless the mint was making cent-sized silver coins for some other country that year.
I seem to remember seeing a few other posts similar to this
they basically said you can create the effect by some sort of school experiment
electrolysis , zinc / silver in a bath
Bradyboy
try weighing it with a scale that has at least a .1 gram accuracy. if you find a scale then post the weight on here. that will help out determining what it is.