While cataloguing a collection of books for its forthcoming antiques auction, Hegarty Auctioneers in Bandon Co Cork found " a rather worn copy of Broncho Charlie Miller's autobiography worth no more than perhaps €10". The book was published in the United States in 1934 and its full title is Broncho Charlie: A Saga of the Saddle – The Autobiography of Charlie Miller as told to Gladys Shaw Erskine.

Now a largely forgotten "celebrity", Broncho Charlie Miller was a star performer with Buffalo Bill's Wild West Show which captivated audiences in America and Europe between 1883 and 1913.

The show featured “cowboys and Indians”, live buffalo, horses, deer cattle and a stagecoach. The show also paid homage to the Pony Express, an early form of postal service in the United States by postmen on horseback.

Such was its popularity, the show was requested to give a command performance at Windsor Castle on 1887 for Queen Victoria's golden jubilee. While in London, Buffalo Bill's Wild West Show also played a series of performances at Earls Court.

Auctioneer Ted Hegarty said the "cataloguer happened to flick through the preliminary pages and pasted into the book was an intriguing pen and ink sketch titled 'This is the way they rode the Pony Express in Earls Court in 1887'."

The sketch is on headed notepaper bearing the address 18 Fitzwilliam Square, Dublin – the home of artist Jack B. Yeats. “Why he drew the picture and how it came to be stuck in a nondescript copy of Broncho Charlie’s autobiography,” Mr Hegarty said, “is one of those imponderable questions that will never be answered, but it elevated the worth of the book” from €10 to possibly €700.

The sketch is not signed by Yeats although his name has been added in ink by an unknown hand.

Jack B Yeats was born in London in London in 1871 but spent much of his childhood in Sligo. He returned to London in 1887 – the year he seems to have gone to the show at Earls Court – and began his artistic career as an illustrator for magazines.

His interest in Buffalo Bill’s Wild West Show isn’t a surprise; he was fascinated by horses and the circus – both subjects of later paintings. Yeats married Englishwoman Mary Cottenham in 1894. The couple moved to Ireland and lived in Wicklow before moving to Fitzwilliam Square. He died in 1957 aged 85.

The book will go under the hammer with an estimate of €500- €700 on Tuesday at 6pm in Hegarty’s Auction Rooms, the Bypass, Bandon, Co Cork. Viewing is from noon today.