Last Friday the station was evacuated when a man arrived with a suspected bomb he had found buried in a garden.
It turned out to be a World War II training shell that was not explosive, but the station was cordoned off for about an hour from 12.45pm before the all-clear was given.
Last week's shell was shaped like a bullet and was 30cm long and 8cm-10cm wide. About 20 police staff were moved outside when officers became concerned about it.
The man found the shell buried in a Henderson rental property garden he was preparing for new tenants. Often shells were taken home by military personnel, buried, and forgotten about, Senior Sergeant Matt Broderick said.
He urged people who find suspicious devices to leave them where they were and call police.