I'll throw in something from out in left field here.
A buddy of mine who follows various scientific journals has mentioned that supposedly steel manufactured after July or August of 1945 has all picked up a certain amount of radioactivity to varying degrees from background atomic radiation. This contamination allegedly makes it unusable for the manufacture of certain types of critical scientific measuring devices. As the supply of pre-atomic steel diminishes (and it's just about gone now) the only remaining source on the planet are the wrecks of WWII warships, and that is why there has been such an effort of late to try and locate as many as possible: to recover the steel.
Not saying I necessarily buy this particular theory, but it's something to consider. Has anyone else heard or seen anything along those lines?