a rigid metal key

The surface of the key is rough, with no sign of corrosion or any other type of damage. It is quite heavy, about five inches long with a large handle and small, sharp wards.

It is a rigid metal key.
It weighs a couple of pounds.

You identify a rigid metal key.
It is an unsellable key.
It weighs one pound and twelve ounces, and it is worth about four celeb.
Its keywords are key, metal, and rigid.