According to the Harlequin website through 2008 Harlequin has shipped 5.8 billion books since The Manatee. Here are three Harlequins from October 1951 when cumulative sales were in the 4 million range.
Originally published in 1950 (New York: Phoenix Press) Boot Hill was one of 17 westerns published that year. Weston Clay was a pseudonym for Thomas W. Ford. Emma Hart (London: Museum Press, 1949 as Our Dearest Emma) was one of three historicals from 1951 and Berlin at Midnight (New York: Greenberg, 1948) one of 34 crime/thrillers. Berlin and Emma were reprinted the next month.
Harlequin 136 back
Harlequin 137 back
Harlequin 138 back