A rare 270-year-old artefact, which may be one of just five left in the world, discovered in a Canberra warehouse was first dismissed as just a ruler.
When Sandie Parkes from the Green Shed stumbled across a 270-year-old slide rule, used for mathematical calculations, she first thought it was a foldable ruler.
"We get a lot of foldable rulers come through, so I thought that must be what it is," she said.
The historic artefact was dropped at the Mitchell warehouse sometime late last year and made its way to the Civic store when Ms Parkes decided to get to the bottom of what exactly the bizarre item was.
She came across the American Oughtred Society, a group "dedicated to the preservation and history of slide rules and other calculating instruments" and United Kingdom Slide Rule Circle, who said the item was one of just five of its kind in the world.
The slide rule is believed to be designed by John Suxspeach and called a Catholic-Organon or Universal Sliding Foot-Rule.
Slide rules were used at the time for mathematical calculations including multiplication, division and trigonometry.
According to the Cambridge University Whipple Museum, Suxspeach was a London schoolmaster who decided to make the slide rule widely available to the public and got the first Royal Patent for it in 1753.
The device had scales, two sliders and brass inserts so it could be used as a protractor or level.
In Slide Rules: Their History, Models and Makers, author Peter Hopp wrote up to 16 slide rules of this kind were made between 1752 and 1755. It is believed there are just five left.
Ms Parkes said she would hold onto the historic item for now but may donate it to a museum. It was a testament to the Green Shed's work "rescuing world treasures".
It is not known who donated the slide rule.
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