"He said it's definitely in there somewhere but we just can't find it."
Mr Booth said one of the last resorts may be digging up paving stones around the plaque.
"That's high risk. We would love to talk to anyone who might know more," he said.
The buried capsule is believed to contain no metal, which has made the process far harder.
Mr Booth said the centenary was not just for the school, but for the Puketaha district as a whole. It reflected how the community has grown.
When the school began in 1916 there were 20 pupils from seven families. That had climbed to around 150 pupils in the 90s. Today the school has almost 300 pupils. Some families have had four generations attend the school.
Two years of planning have gone in to the event, which will take place over two days.
Kicking off on Friday there will be a registration and tour with a presentation from the children.
"The classrooms have been divided into the different eras. Part of that will be what would it have looked at in different 20-year periods," Mr Booth said.
Displays will include stylised classrooms and outfits from the different eras.
"Learning looked very similar from the 60s through to the 90s. The desks changes slightly but you were in rows with the teacher at the front of the class room who delivered information," Mr Booth said.
"Learning looks and feels very different to how it would have in the past. It's less autocratic and hierarchical."
He said the only thing that had not changed was the schools principals of aim high, celebrate differences, show fairness, have integrity and show care and respect.
A cake to celebrate the 100 years will be cut by one of the first and the oldest surviving student at the school, 92-year-old Inewa Ward who joined the school in 1930 at age 5.
"There were only about six of us there at the time, it grew quite a bit," she said.
Inewa remembers a time when half the children would ride horses to school and the whole thing consisted a single room where all age groups were taught at once.
"Those teachers, I don't know how they did it," she said.
Today there are four learning environments, each roughly the size of three classrooms.
"I remember hot milk at the gate, it got hot in the sun and all creamy. It was horrible," she said.
Inewa recalls the single fire sat in the back wall of the classroom - the only heating for the children in winter.
Ex-student Bryan Mayall, who was at the school a decade after Inewa and has been part of the committee organising the centenary, remembers the school dances, when all the tables would be passed out of the windows to make room.
The school centenary celebrations will run from September 23-24 with the main event starting on the Saturday from 10am. Visit www.kmwebsitedesign. co.nz/centenary for more information on the centenary. Attendees need to register.