That "square piece" is a crossbolt. Whether it works, or is even necessary, is another whole wrangle, but that's what it is. If that gun is an Ugartechea field grade boxlock--and it works--I'd say you did well for 325 of those little northern rasbucknicks! Would need more/clearer pictures to know if you did better than well. Main issue with a gun like that is how well it functions, including shooting to point of aim and patterning. Does it have ejectors (can't remember)? Do they eject reliably? Has it ever doubled? Shoot where you point it? Stuff like that.
