Painting fixed under glass 19th century

Painting from the early 19th century. Technique / painting under glass is a unique technique because the work is done on the back of the glass. While on a canvas you sketch the composition in broad strokes and then do the flat areas of color to gradually finish with the details, in reverse glass painting you do the opposite. Unlike the normal technique, which is to do the details (the nose, the eyes, the flowers) before the background (the face, the landscape), the viewer must look at the finished work on the unpainted side of the glass plate.