Superposed are tricky to buy. They were the favorite of a lot of competition shooters, and many have been shot to death. Make sure the barrels ring true, because a LOT have loose barrels and/or ribs.
There's also the issue of salt wood. More guns than not had salt wood. Find a piece of wood with no finish (under forend metal, under recoil pad, etc) and do the silver nitrate test. If it passes, you're good, if not...unless you REALLY know your stuff; pass on any Superposed that fails the test.
