The bronze and copper plaque, which is believed to have disappeared from Walnut Park sometime after Dec. 21, was likely stolen for the value of its metal, Petaluma police Sgt. Ralph Evans said.
The plaque measures 25 inches by 30 inches, and is an inch thick. It had been placed in a concrete base near the park's gazebo sometime in the mid-1970s, Evans said.
Noriel said the thief or thieves may have removed the plaque from its base with an electric saw because electricity is available near the memorial.
Petaluma Parks Department employees working in the park on Tuesday discovered it was missing.
Local veterans are raising funds for a new plaque that will be better secured in a new memorial. The replacement will cost about $1,000, Noriel said.
Already, the managers of the Les Schwab Tires stores in Petaluma and Santa Rosa have pledged a total of $1,000, and Powell's Sweet Shoppe in Petaluma has pledged to match donations up to $500, Noriel said.
The Petaluma Firefighters Local 1415 union also offered to donate money, and a veteran has pledged $1,000, said Liz Cohee, the museum's coordinator.
Police are contacting local salvage yards to see if the thief has tried to sell the plaque, Noriel said. Anyone with information about the theft is asked to call police at (707) 778-4372 or the museum at (707) 778-4398.
Tax-deductible donations may be sent to the Petaluma Museum at 20 Fourth St., Petaluma CA. 94952.