Well, I'd say the feat is fair but high-end for Erik. He specifically stated that he could sense the particular metal involved, he was highly motivated since he was trying to prove he was not a douchbag. All of that said, it's not a speedfeat in the traditional sense - he used his rather awesome powers to pick up a totally unique material that he stated to have "tagged" the first time that it passed. The fantastic power feat part is that he managed to bring back in a few days a planet-buster object that had been moving at superluminal speeds for months. The facts that he had days to plan the arrival, however, is what makes this decidedly not a combat speed feat.
I typically give Magneto low-mid bullet-timer speed with his powers - he has plucked bullets out of the air (not shielded them, but caught them) enough times that I'm willing to go there. I think that most people agree, in general.