Why I say alum, is that I used some chome polish on it, and the residue was black.
It weighs 5 oz, while my slightly longer SO weighs 5.3 so it is probably just a plating, as you said. I have one on ebay, but picked up 3, and can get more.
I had tried a fridge magnet on it yesterday, and thought it was not magnetic, but I used a real one today, and it IS magnetic.