The silver pocket watch contains a delicate, hand-annotated love note written by Armour on a piece of paper hidden inside the case.
The “pair-cased” watch contains a hand-pierced paper insert with a twin love-bird and heart motifs, and the initials “R” and “J” inside them – which experts believe refer to Rabbie and Jean.
On the back of the watch, which experts say is in excellent condition, the words “Robt Burns Mauchline” and the date 1786 are engraved.
Phil Gregory, spokesman for the auctioneer Lyon & Turnbull, said the watch came from a private collection and the seller had opted to remain anonymous.
He said: “I’ve held the piece myself, and it’s in amazing condition. You would not have thought it was the age it is.
“The piece of paper that sits inside it is very pretty, and the ink that the ‘R’ and a ‘J’, is written in is really fresh.”
Describing the watch as “quite chunky”, he said it would have been “a special piece” for Armour to have given the Bard.
Mr Gregory said: “It is a lovely item. This was from London, which is quite an extravagance, as they could have easily had one made in Edinburgh. But we know that they went all the way down to the city to have this one made by a really good watchmaker, so it is obviously a very special gift.”
He added that given the level of international interest from both museums and private collectors, particularly from the United States, the auction house hoped the watch would fetch more than the £2,500 estimate when it goes under the hammer next Wednesday.
The Belle of Mauchline, as
Armour was known, had a remarkable memory for quoting verse, and Burns often read his work to her and greatly valued her opinion.
She raised nine children with the poet, and Burns’ love for her was the subject of many of his poems, including the immortal lines from Of A’ The Airts: “There’s not a bonie flower that springs, By fountain, shaw or green; There’s not a bonie bird that sings, but reminds me ’o my Jean”.
The story of Burns’ relationship with Armour was torrid, according to historians. Armour is said to have been a loving but long-suffering wife.
Murdo Morrison, spokesman for the Robert Burns World Federation, said he believed it was important the romantic watch stayed in Scotland.
He said: “It’s very exciting that this watch has surfaced. Our hope would be if it’s sold it will be well looked after by whoever buys it, and that it would remain in Scotland.
“Jean Armour was a very special woman, who forgave Burns on more than one occasion when most women would have told him where to go.”
Burns and Armour met in Mauchline, Ayrshire, in about 1784. Within a year she was pregnant outside of wedlock, prompting her appalled father to remove her to Paisley and forbid Burns from seeing her again.
Even though the then struggling poet had agreed, under duress from the church, to marry her, Armour’s father refused to allow the union to go ahead.
Burns turned to a number of other women for solace and even considered a move to Jamaica to declare himself single.
Jean went on to give birth to twins, and was disowned by her family. She soon fell pregnant by Burns again and by 1788 was destitute, and soon due to deliver another set of twins.
Burns made a second attempt at marrying Jean that year. As he was by now a relatively famous and successful poet, his prospective father-in-law’s opinion of him turned in his favour and the couple wed.
The last of their children was born on the day of his funeral in July 1796; Jean outlived him by well over 30 years, long enough to see his reputation become one of national acclaim.
The watch will be auctioned in a specialist sale at Lyon & Turnbull in Edinburgh.