It was consigned for sale at Trevanion & Dean on May 19 by a lady whose husband had been given it to keep good time while working on a building site 60 years ago.
The Grana is considered the hardest to find of the Dozen, with perhaps as few as 1500 made by this otherwise routine maker.
Seven Grana watches have been sold at auction since 2012 at prices ranging from £3500- £5500. Christina Trevanion estimated this one, that had some imperfections, at £2500.
However, after bidding between two collectors, it sold to an overseas buyer for what was deemed a record price of £9000.