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.
Search for Edward Ardizzone books [amazon]
Daphne's blog on children's books shows her to be quite an Ardizzone fan [daphne.blogs.com]