After I posted this out came another astrolabe story in the press: 	

Ancient calculator in 'record' sale
http://www.breitbart.com/article.php?id=paQuadrantWed16CalculatorAuction&show_article=1&cat=tech

"A 14th century scientific tool, which was the "pocket calculator" of
its age, has sold for a "world record" price.

The astrolabe quadrant ... an anonymous telephone bidder at an auction
at Bonhams in London...

Auctioneer Jon Baddeley said: "This is an extremely rare piece. Prior
to its discovery in 2005, there were only seven others known about.
Now there are only eight known in the world, in its area it's gone for
a world record price."

The astrolabe quadrant has been dated to 1388, the period when
Geoffrey Chaucer began to write The Canterbury Tales, and was used for
telling the time, surveying, mapping the stars and making calculations
such as measuring the height of buildings or the depth of a well.

Made in England, it is one of only eight known examples in the world.
It is also one of the oldest and smallest in existence.

The brass instrument was discovered underneath a series of clay floors
during building work in 2005 to extend a restaurant in Canterbury,
Kent, known as the House of Agnes - a 17th century inn on the road to
London, just outside the city..."

There's more at :
http://www.breitbart.com/article.php?id=paQuadrantWed16CalculatorAuction&show_article=1&cat=tech

Maybe it was Chaucer's? He wrote a treatise on their use according to
Wikipedia. "The English author Geoffrey Chaucer (ca. 1343–1400)
compiled a treatise on the astrolabe for his son, mainly based on
Messahalla." (founder of Basra, Iraq) - Wikipedia

George Myers