The painting is The Iron Rolling Mill (1872-75) by the German artist Adolph Menzel. I wrote an essay about it as an undergraduate. Menzel draws on the traditional iconography of the forge, but produces a thoroughly modern painting representing the everyday life of workers in Upper Silesia whose days are ruled by the demands of the modern machine age.
I saw this painting in an exhibition in the Neue Pinakothek in Munich a few years ago. I love the flame hair of the lady, so in tune with the subject of the painting, and the chevron pattern on her jacket. But if you would like to see the painting without the observer, here it is: