With a bit of research, I've discovered that the Broadwood grand #3448 is pictured on page 87 of the English version of Ernest Closson's The History of the Piano, after finding a reference to it in an article by Kenneth Mobbs, "Stops and other special effects on the early piano." (Early Music, Volume 12, No. 4, November, 1984; footnote #6, page 476.)
