A previously unseen painting of a pet dog by Édouard Manet will be sold for the first time at an auction in Paris next month. The French modernist artist dashed off the small work in 1879 as a present for Marguerite Lathuille, the daughter of a Paris innkeeper whose portrait he painted around the same time. For the last 140 years, the work has remained within the Lathuille family, which has refused previous offers to sell it. The art expert Frédérick Chanoit said the painting, measuring 32.5cm by 24.5cm, had been produced in 20 minutes and is an example of Manet’s technical skill. “It is not one of his chefs-d’œuvre [masterpieces] but it a marvellous interpretation of Manet’s skill; a wonderful symphony of tufts and touches that show his pure genius,” Chanoit said. “It is different from his classic works, but it demonstrates his technical skill as a painter. The fact that in a short amount of time and brushstrokes, with minimum of means he could produce this picture of a little dog, that is a ball of fur but full of movement with living eyes is extraordinary.” Chanoit said the painting had been catalogued and written about, but had not been publicly seen since it was produced. “We have letters that show in the 1920s an art dealer wrote to Marguerite begging to buy it from her but she refused. It passed directly to her children but until now they did not want to sell it,” Chanoit said. The oil on canvas painting, named after the dog, a griffon called Minnay, is one of a series of eight dog paintings Manet produced between 1875-1883. The animal belonged to Marguerite, whose father was Gauthier Lathuille, the owner of a cabaret and later restaurant that featured in other Manet paintings, including Chez le Père Lathuille, in which Gauthier appears in the background. As well as painting Marguerite’s portrait, which now hangs in Lyon museum, the artist also completed a pastel portrait of her brother Louis, now in a private collection. Manet was a frequent visitor to the Lathuille establishment on Avenue de Clichy in the Batignolles district, an area popular with the impressionists. “Still owned by the descendants of the dog’s owner Marguerite Lathuille, this portrait is unique and has remained unknown on the market for over 140 years,” say the auctioneers, Drouot Estimations. The work will be sold on 26 February in Paris and will be available for viewing for two days before the sale. It is expected to fetch at least €280,000 (£248,000).