Expected to make £500-£700 in the Antiques and Fine Art auction at the Exchange Saleroom in Driffield last Friday, the final sale price was actually £1,150.
The blackened old tankard was so tarnished and filthy when the boy's father brought it home in a box of bits and pieces from a garage clearance that neither the writing nor the marks on the piece could be distinguished.
It was only when the teenager cleaned it up that it became clear it was a trophy awarded by a wealthy 19th century East Riding landowner for an early county ploughing competition and that it was in fact almost two pounds of hallmarked solid silver.
Before the auction, Andy Spicer of Driffield-based Spicers Auctioneers said: “It is terrific find. Our vendor initially thought it was just a very mucky brass piece. He gave it to his son who is apparently interested in old things and it was only weeks later when he got round to cleaning it that things started to get interesting.
“The inscription records that it was donated by James Hall of Scarborough Hall near Leconfield as the prize in a competition for the best plougher amongst farmers sons that was organised by the East Riding Association at Warter Wold in 1845. The winner was William Walker of Arram.
“In fact the tankard is much older than that. Other marks revealed by the clean-up have enabled us to establish that it was made by the London silversmith James Manners in 1734, so it was already an antique when James Hall donated it for the competition.”