"The UFW banner was one of my favorite stories to work on," said Lucy Blackburn, producer of "History Detectives." "A lot of the country isn't as familiar with the work of Cesar Chavez as most Californians are, and the UFW banner story was a great opportunity to bring that history up."

The banner, made of velveteen and satin, features an image of the Virgin of Guadalupe and the farm workers eagle, the symbol for the United Farm Workers. It is rumored to have been carried at the head of the famous Delano Plan march during the grape boycott, which began in 1965.

In the march, Cesar Chavez, then 38, led several dozen protesters on a 230-mile route from Delano, Calif., to the steps of the State Capitol building in Sacramento. They sought better living conditions and rights for Mexican-American farm workers.

The Delano Plan march lasted 25 days. Citizens from every walk of life joined the marchers at various points along the route. When they arrived at the State Capitol building at noon Easter Sunday, more than 10,000 supporters waited to meet them.

Pictures of Cesar Chavez and his fellow protesters walking beneath the banner, alongside articles about the march, were featured in California newspapers for the 25 consecutive days of the march.

The banner's donor is the widow of a man who participated in the Delano Plan march before he was married. He later told his wife the story of the march and the role the banner played She relayed his story to Susan Sherwood, acting director and archivist at SFSU's Labor Archives. The "History Detectives" hope to confirm whether the banner is in fact the one carried in the 1966 march, and they have spared no effort to find out.

"Our detectives traveled to Sacramento to speak to people who knew the donor," Blackburn said. "We went to Harvard University to meet with a labor historian who was part of the march. We also talked to a curator at the Mexican-American Museum in San Francisco who examined the iconography and historical symbolism of the banner and uncovered information about the use of banners in political marches."