Some artists’ colourmen applied stamps to the back of ready-to-paint, stretched canvases in standard sizes. The stamps varied over time (with design and address changes). If the stamp’s date has been established, it may help date an undated painting, or even to help identify a forgery if the stamp date does not correspond with the artist’s dates. This stamp of the British artists’ colourmen firm of Winsor & Newton dates to 1884-1904.