Showing the Adoration of the Magi, it was based on the central panel of Rogier van der Weyden's 15th century St Columba Altarpiece, now in Munich's Alte Pinakothek.
The 4ft 9in (1.45m) high by 5ft 3in (1.6m) wide window had been removed from an old North Cornish house and the private vendor believed it was acquired in Eastern Europe by a relative during the Second World War.
A specialist at London's Victoria & Albert Museum consulted by the auctioneers said the size of the lead glass panels dispelled any wishful thinking about an early date. He believed it to have been made c.1850, shortly after the original triptych had been rediscovered.
Possibly the work of the Royal Bavarian Stained Glass manufactory, it topped this 1000-lot sale selling to a private buyer at £5000.
