It’s from the embarrassing-as-hell album Tintin au Congo (1931 originally, 1946 in color).

The story of how Hergé evolved from ‘know-nothing, Belgium insular’ to ‘evolving world man’ is touched on pretty well in Ampton’s articles, I think. [link]

EDIT: Despite my criticism above, what we’re looking at here is in fact a nice example of polished LC (ligne claire), something which went on to define much of the artform and storytelling sense of BD for… well, it’s coming up on 100yrs now. oO