OAKLAND -- About 400 parking meters have turned up headless this year, in a likely indication that some enterprising vandals are trying to make a few dollars -- but they're mostly coming up empty, city officials said Monday.

"We periodically have a spate of these when the economy turns especially bad," said Karen Boyd, spokeswoman for the city administrator. "People will saw off the meter heads thinking they can break them open and get the quarters."

Most meter heads are so sturdily built, however, that when officials find them discarded, they're rarely broken open, Boyd said.

"We first heard about these showing up when the San Leandro police gave us a call and said, 'Hey, we found some of your meter heads,'" Boyd said. Few were actually broken open, she added. The most recent rash of headless meters turned up on Grand Avenue, she said.

Meanwhile, the city's been in the process of swapping out the old-fashioned, single-stall, coin-eating meters for the multi-space meters that take credit cards and give motorists a receipt to leave on their dashboards. As a result, the city has plenty of the old meters in storage to replace the sawed-off machines, Boyd said.

A new meter head costs about $300, Boyd said, but a new pole is just $15 and the city is now installing sleeves over each new pole, which can spin around the pole and make it near-impossible for a saw to get its teeth to do any damage.