First thing is to check the bilge for big nuts and bolts to see if if it is a bolt on or integral keel. I saw a photo of a guy repairing his keel and it clearly was integral. They tend to be much thicker, but if the boat is in the water that is tough to check. The owner should know. I know a good surveyor for sailboats in MA/RI if you need one. As far as steel vs. lead it is impossible to tell as the pieces are encapsulated in resin. The bilge for such a keel is much deeper than what you are used to, so there is no real way to tell that I am aware.