If my memory of chemistry serves me correctly, the mirror finish should
be removed quickly by nitric acid, which will turn the silver to a
solution of silver nitrate.  The only problem is that it my be difficult
for an individual to get nitric acid, as explosives can be easily made
from it, and the by-products of its reactions are often dangerously
reactive themselves.

I don't think I'd try it myself.  Why not look for an amateur astronomy
site on the 'Net?  They make a lot their own telescope mirrors, which
sometimes need to be re-silvered.  Perhaps they have a safer way to
strip the silver off.

Dave Vincent