John Elmslie of Toronto shares this in the Boing Boing Flickr pool and writes,
Vintage paperback. “A Harlequin Book”, Toronto, 1951. So Harlequin was publishing more than romances in 1951. The original paperback book is quite faded looking. The scanner pepped it up quite well, even though I hadn’t asked it to. I’ll have to look into that. :)