A rare collection of Jacobite glasses, representing the lifetime's work of the world's leading authority on their manufacture, will go under the hammer at an Edinburgh auction house next month.

Bearing motifs and inscriptions in support of Bonnie Prince Charlie, the glassware once represented potent symbols of allegiance to the Jacobite cause for the families or societies who drank from them. To supporters of Britain's 18th-century Hanoverian monarchy, they would have signified treason.

In the fraught atmosphere of the 1740s, when Prince Charlie - or the Young Pretender - marched an army from Scotland as far south as Derby, it was wise to keep allegiances secret. The five Jacobite glasses on sale are decorated with symbols of the cause, such as roses and rosebuds, and oak leaves, or Latin words such as Redeat, meaning “may he return” and Fiat, “Let it be”.

“The glasses have always been rare and expensive,” said Dr Geoffrey Seddon, who is selling his collection. “Jacobite glasses are the largest group of 18th century commemorative glasses and the Jacobite movement occurred during a pivotal period in this country's development. They are treasonable, in effect, and it is this history that makes them so valuable.”

Dr Seddon, 77, a former GP from Redditch in the West Midlands, began collecting 18th century glassware more than 50 years ago, and started to specialise when he purchased his first Jacobite goblet. He soon realised that the engravings were easy to fake, and that forgers could quickly increase the value of plain 18th century glassware by cutting in a motif of the Young Pretender,

“Engraving involves the removal of material, and that makes it very hard to date. Fairly crude forgeries can increase the value of a glass from a few hundred to a few thousand pounds,” said Dr Seddon.

By analysing a large number of glasses Dr Seddon was able to show that more 60 per cent of the originals were produced by just five engravers, all of whom were probably based in London. Ironically, one of the first forgeries he uncovered was the glass he originally purchased.

For all their beauty, the glasses are symbols of a bloody episode in history, whose constitutional repercussions are still being debated. The Jacobite rebellion of 1745 had its roots in the Glorious Revolution of 1688-89, which forced the Catholic King James II and VII from the thrones of England and Scotland, to be replaced by the Protestant William of Orange. Support for “the King over the Water” lingered for generations, particularly in the Scottish Highlands, in parts of Lancashire, western England and in London.

By the 1740s, the most common Jacobite symbol was the rose, shown in full bloom to represent James Francis Edward Stuart, “the Old Pretender” and two buds on the stem representing the his Stuart heirs, Prince Charlie and his brother Henry. The oak leaves are a symbol of Charles II who reputedly hid in a tree to evade Cromwellian persurers after the Battle of Worcester.

Dr Seddon's collection is said to be comprised of “exceptional” examples and each piece is likely to reach prices in excess of £1,500. Also at auction is his collection of photographs, which exhaustively detail every Jacobite drinking glass he has assessed, and a signed copy of Dr Seddon's definitive book, The Jacobites and their Drinking Glasses.

Though English in origin, the collection forms part of Bonhams' Scottish Sale, which is being held at the auctioneers new premises on Queen Street, Edinburgh, on August 27.

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