A Hastings District Council spokeswoman said the two items were in a safe taken out during the demolition in the kitchen of the Municipal building.
"They might have disappeared forever if not for the curiosity of a local scrap metal dealer keen to find out what was in a safe that had been dropped off by the Opera House precinct contractors", she said.
Bristow said Knight took it upon himself to find out what was in the locked safe before it was sent away, prying it open with an excavator and cutter.
"Tim went the extra mile. We knew we had found something special when we saw what was inside."
An engraving on the trowel identifies it as having been presented to Hastings Mayor William M Hart by Stanley Brothers to commemorate the laying of the foundation at the Hastings Municipal Building on February 9, 1916.
A small plaque on the scissors box noted they were presented to Mrs W Hart "mayoress" on the occasion of opening Russell St, formerly named Station St, Hastings, on October 16, 1922.
Hazlehurst said she was very grateful to the team at Scrapit for finding the community treasures.
She said both pieces would be put on display when the project was complete, probably alongside other historical treasures found throughout the Opera House strengthening project.
