As part of his teaching duties at the Metropolitan School of Art, Orpen gave lectures in anatomy. In the picture we see the artist cribbing from a book on the desk doing his best 'to do his duty'. However, having misplaced his Gray's Anatomy, the anatomical bible, 'the only book worth working from', he has to make do.
The gentleman seated in the audience appears to be Richard Orpen, the artist's brother, an architect by trade, but also a fine watercolour artist in his own right and an important figure in the Dublin Art Scene on the administrative side in the early part of the century.
The letter, because of the reference to the Modern Art Gallery, must date to at least after January 1908 when the Gallery opened. It could well be about December 1908, as Robert O'Byrne, in his recent biography of Hugh Lane, mentions that in early December 'the premises were briefly closed for cleaning and rehanging' (see R. O'Byrne, Hugh Lane 1875-1915, Dublin, 2000, p. 110).