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The antipollution device bolted onto your car's exhaust pipes contains platinum, an expensive metal. Some recycling shops will pay $200 for a used converter — whether it comes from a junked vehicle or was freshly sawed from beneath a Toyota Land Cruiser at the Stanford Shopping Center. I typed up the best parts of a not-online report by the San Francisco Daily Post:

From San Francisco to San Jose, scores of unlucky car owners are starting their engines only to hear a loud roar that means their catalytic converter has been cut right off the bottom of their vehicles. It commonly costs $1,000 to $2,000 to replace the anti-smog device. "It's got to be organized," said Palo Alto police Agent Dan Ryan. "The thieves have to take it to someone who can melt it down, extract the platinum, and then resell it on the open market." [Platinum, used inside the converters, sells for above $2,000 per ounce.] AAA-approved muffler shops have taken to welding steel bars over the converter to protect it — usually after the owner has already suffered one theft. But the best advice, police say, is simple — don't park on the street.

(Photo by AP/Robert F. Bukaty)