Superposed were made in Belgium (and some in US I believe)--it was John Browning's last gun that he designed. Production stopped in 1960, but you could/can still get one from the custom shop. The Citori was the follow on design--meant to be made in a more mass-produced manner, and currently made in Japan. Both are good guns, but the Superposed was hand-built and fitted, and has more parts and is more complicated, and wouldn't normally have replacement chokes unless someone added them.
"Adversity does not make a man--it reveals him"