Legal Seafood magnetic knife puzzler (submitted to Car Talk)

Q. A bunch of mathematicians eating dinner at Legal Seafood in Kendall Square (myself among them) noticed that some of the knives were slightly magnetic. When we pointed this out to our server and asked her what was up with that, she said "You're not the first people to notice this, but I have no idea what's going on; I'll see if anyone in the kitchen knows anything about this." When she came back with our food, she said "I've found out the answer to your question, but I'm not sure you want to hear it." What was the explanation for the magnetic knives?

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