You just never know what you've got in the shed. This horary quadrant was found in a bag of old pipe fittings in a shed on a farm in Queensland, Australia, forty years ago. Last year the owner of the quadrant was surfing the internet and came across this article where he recognised not just the same tool, but the same stag-coronet insignia that was on his quadrant (he thought it was an astrolabe) signified it was made for King Richard II (of England).

He subsequently contacted the British Museum, which identified the item sitting on his desk for the last forty years as a 1396 horary quadrant. It will be auctioned next month and is expected to fetch between GBP150,000 and GBP200,000.

Perhaps even more remarkably, the simple quadrant which is used for telling the time, and had been in use for at least 1500 years prior to the making of this peice in 1396, has turned out to be the second oldest British scientific instrument ever discovered, the oldest being the Chaucer astrolabe, dated 1326, which is housed in the British Museum.

Dated 1396, the quadrant is one of four similar quadrants found to date (the others have been dated 1398, 1399 and circa 1400 respectively), two of which can be found in the British Museum, and the other in the Dorset County Museum, Dorchester.

The horary quadrant was the most commonly used way of telling the time prior to the invention of the clock. One edge of the quadrant was pointed directly at the sun, and a plumbline attached to the centre of the quadrant signified the hour of the day.

All four of the above mentioned quadrants were divided into equal hours, meaning they would only be accurate at one specific latitude, and all four are accurate at the latitude of London.