excerpt from the National Gallery website

“From around 1842 and into the 1850s Courbet painted about 20 self portraits in which he presented himself in different guises, often referencing Old Master paintings he copied in the Louvre. This portrait is a reduced version of The Man with the Leather Belt (Musée d’Orsay, Paris), which Courbet painted around 1845–6 and almost certainly exhibited at the Salon of 1846.

Courbet painted replicas of at least three of his self portraits and it was previously thought that he also painted this version of The Man with the Leather Belt. However, although this portrait is close in almost all details to the original, there are major differences between them. In particular, unlike the very finely painted Orsay picture, the brushwork is more cursory and less detailed.

Recent research into the picture’s support and a label on the back also suggests that the painting dates from the early 1880s, and therefore could not have been painted by Courbet himself, who died in 1877. It is instead a copy by someone who had an excellent understanding of the original.’