Three books in 1953 were signed by "ATR". A likely candidate is Aileen Tyrrell Richardson (1916-2005). She was a graduate of the Ontario College of Art, lived in Toronto and was an active mid-century illustrator for Canadian magazines, including Chatelaine, and books.
Signature - Harlequin 216
Harlequin 216 - February 1953
Harlequin 230 - May 1953
Harlequin 234 - June 1953