I looked this lens up in Sartorius during my lunch break. The filter size is listed as 48mm (actually, the third version, which I have, has a 49mm filter and the latest goes down to 46mm) and the hood's code number is 12501.
Your lens (which is the first one produced in Canada) should be the second version of this lens. The first was produced in Wetzlar, and the protruding rear element blocked the meter reading off the white spot on the curtains.
Again... consult with Kevin. He may be able to recommend an alternate hood. In any case, you may want to keep this lens. I just got back my first 28mm slides and the reach of these babies is... nicely large!
Of course, it's a wide-angle, duh! 🙄
Let us know when it arrives! 🙂