See if the grinds are the same and the blade is straight and the clip matches on both sides. Liner lock-up and fit. Locks have been known to fail that are on the left edge of the blade, on the center of the blade or all the way across the blade. If these two things are correctly done the lock will hold, if not, the lock will fail no matter where it sits on the blade. So the only way to know is to apply pressure to the blade and see if it holds.
Every customer has a preference as to where they want to see the lock.
Check for sharp edges and finish of the screw slots. Check the blade grinds as above. Daggers are often challenging in this regard. Many believe the balance point should be around the guard while, for swords, from the guard to 10 inches max. A hand-rubbed finish should be a continuous set of lines with no fuzzy brush marks.