Could be Factory Repair. As for it being upside down, don't forget that most of the big armouries used to rack their No5's upside down - on the muzzle - with the bolt open, just to preserve the old rubber butt pads. The heat used to cause the oil to run down into the trough that the butt plate sat, soften it and the weight of the rifle would just squash the rubber to a sticky gooey mess. An easy fix UNLESS the bloody male/female thread of the butt plate screw had corroded together. Then you have to rip off the old rubber pad and cut the screw. But even that was a chore on some because on some No5's, there was a steel plate between the butt and the rubber pad. If this was rusty too and the butt plate had stuck to it it was a drill it out job. Good idea until the whole bolt rotated with the drill!
Hey......... that's brought back some memories!