Familiar with this model in particular no, but worked on a lot of models of firearms 40 years ago. Memory serves as well as memory serves these days, none of burned in it anymore, especially the various part designs. The part is not identifyable from the picture for me, no description/relative size, where it fell out of, where it might fit back into, etc since it's not in hand. Can't tell if it is a pin, retainer, rod, dog or stop for sure. As I said further complicated on a model that has model revisions where parts design may have changed over the years of production. Maybe the firing pin itself (slotted flat earliest, round later), maybe something else. Many action parts could prevent full breech bolt travel if the stars align just right.
What I do know for certain, "welding" any firearm part is a last resort and certainly not the best choice. Not something we did in our gunshop except very rarely. We usually made new replacement parts ourselves if they were not readily available. The exploded diagram I linked is a company that sold parts for them. Numrich might as well, and other companies. Far better choice would be to buy a replacement part from one of them.
Just my opinions and guesses, YMMV.
