The time capsule was found stashed behind the cornerstone at Cleveland Elementary School after John Weidinger -- a Cleveland alumnus and school volunteer -- found a reference to it in an old newspaper, the San Francisco Chronicle reported.
The box was opened Wednesday, just over a century after Mayor P.J. "Pinhead" McCarthy put it in the wall at the school during a ceremony reported by the San Francisco Call in a single sentence.
"Had I not found that one sentence, maybe we might have lost that part of San Francisco history," Weidinger said.
He removed and opened the box as students watched, the Chronicle said.
The box contained a variety of documents, including a salary schedule for teachers in San Francisco and the 1909 California school law. There was also a letter from the Excelsior Homestead Improvement Association to a future mayor of San Francisco.
"The city of San Francisco has just about recovered from the effects of the great earthquake and fire of 1906 and is now on a fair way to gretaer prosperity than ever," the organization said, in a letter that was not completely free of typos.