So the Domestic Interiors Database is nearly impenetrable, with pull down menus offering searches by "Dwelling - Specified Social Level" and such.
Randomly trying to recreate Andy's search, I stumble across this excerpt from James Kenward's 1955 autobiographical children's book, The Suburban Child, which was illustrated by Edward Ardizzone:
[p. 61] The custom, which survives to this day in remnants of true Suburbia, was for the yacht to be berthed on the nursery window-sill. It was the outward and visible sign of a small boy in the house; and thus, glancing up at the windows as you passed by in the street, and noticing the numbers and sizes of the yachts displayed, you could estimate the numbers and [p. 62] sizes of the male children living there. I remember my father doing this once. It was in answer to the question: “What is a detective?”Has anyone ever heard of this "custom", or was it limited to pre-WWI suburbs south of London? Or was it not a custom at all, just an illustration of the powers of deduction?
Anyway, while trying to track down a copy of The Suburban Child--which would be a helluva lot less enticing a title if it had been published in 2005, funny what a half century of degrading homogenization'll do--I searched for Ardizzone, who turned out to be a pretty well-known and prolific children's book illustrator in his day.
His own series, Little Tim, shows his lighthanded, sketchy style, but they're not the ones that floored me.
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Search for Edward Ardizzone books [amazon]
Daphne's blog on children's books shows her to be quite an Ardizzone fan [daphne.blogs.com]