Metallurgical studies show that it was constructed of a type of iron that could not have been made under present atmospheric conditions. To verify that the hammer was made of metal, they cut into one of the beveled sides with a file. The bright metal in the nick is still there, with no detectable corrosion. The unusual metallurgy is 96% iron, 2.6% chlorine and 0.74% sulfur (no carbon). [source Simon John Roy Laxon]
As soon as the Carbon Dating results come out, then we'll all be like, "Wow!" I'm sure.