LONDON.- It is not every day that a lost masterpiece resurfaces and when it’s a work by the preeminent 18th century animal painter George Stubbs (1724-1806) interest is bound to be high. Until recently, Stubbs’ A black and white spaniel pointing was considered lost. In fact, it had been hidden away unrecognised in a collection overseas and its re-emergence is already capturing the attention of collectors. The portrait, which leads Bonhams Old Master Paintings sale in London on 6 July, has an estimate of £200,000-300,000.

Although Stubbs made his name as a painter of horses for the grandees of racing and horse breeding, he developed an equally lucrative career as a painter of dogs – often as commissions from the aristocratic owners of the horses. As art critic Susan Moore, writing in the summer edition of Bonhams Magazine explains, “His clientele was delighted that he was prepared to treat their hounds, working dogs and lapdogs with equal individuality, dignity and respect.”

His most productive years as a dog painter were the 1770s and he exhibited 15 canvases at the Royal Academy over the decade. A black and white spaniel has been dated to the latter part of this period. Stubbs often gave generic titles to his portraits of dogs rather than identifying them by name or breed. In the case of the painting for sale what is now recognised as a spaniel is in the act of "pointing" at game, standing characteristically rigid with muzzle stretched toward the bird and one foot raised.

Lisa Greaves, Bonhams Head of Old Master Paintings, said: “This is a wonderful painting and a great rediscovery. As with most Stubbs dog portraits, the focus here is all on the spaniel itself which occupies and dominates the entire canvas. The painting, is also highly typical of Stubbs working methods particularly in the way in which the exuberantly feathered tail – he clearly took a special delight in painting tails – is portrayed against a plain and darker background.”

Other highlights of the sale include:

• Portrait of a Collector, standing three-quarter-length, before a draped table with statues, medallions and books by Bartolomeo Passarotti (1529-1592). While part of the Esterházy collection (which was dispersed in 1870), this portrait was ascribed to Giovanni Battista Moroni, but in 1981 it was identified as the work of the Bolognese painter and portraitist Bartolomeo Passarotti. Typically, the artist has made full use of the narrative and expressive potential of the figure's hands. He has also paid particularly close attention to the detail of the face with the sitter's facial features and beard meticulously depicted. By contrast, the objects in the background are more loosely and freely rendered. Estimate: £200,000-300,000.

•A trompe l'oeil still life of a framed letter rack with a copy of Antony Thysius's Sondaghsche uren, a letter, a Delft Almanac, two combs, a quill, a portrait miniature and other objects (above), by Edward Collier (1640-1708). This outstanding and well-preserved example of Collier's work dates from his mature period when he was working in Leiden between 1702 and 1706. It compares closely to two other depictions by the artist of framed letter racks from the same period, both with portraits of Erasmus and both of which are dated 1703. Estimate: £100,000-150,000.