If the bore's not deeply pitted and does not have to be honed a whole bunch, that gun just might surprise everyone. Certainly looks a mess now, but as noted above, if it does not reach .010 beyond the specified bore diameter, it might pass proof as originally marked. Even if more than .010 has to be taken out, if sufficient wall thickness remains, it might still pass proof but at the next larger gauge. That is to say, if it started life as a 12, it might end up passing proof as a 12/1.