Ah, have you "measured" the angle on the upper side of the tube or on the bottom side? The tube is a bit "tapered" or "oval" and one side looks more leaning that the other.
A stem for a 1" threaded steerer has a 22.2mm diameter, and a stem for a 1-1/8" has a 25.4mm diameter, am I right? If it is right, I need a 1-1/8" stem. :)