This book appears to be a 1950s reprint. On the back is a long list of all the Beatrix Potter Books. Thus, it can be no earlier than the latest title listed. There are also codes on the copyright page that imply a 1952 printing date (left of the hyphen) if I am interpreting that correctly. Teh book looks like a 1950s edition and that could make sense since the first part of the baby boom generation (born 1946-1952) would be about 4 in 1952 and the book could have been purchased in the year following the date code. 

The 1909 publication date is not true to this actual printing. In other words, discovering a true date is often a mystery hunt.

The book itself has some significant damage to the dust jacket and appears to have been price clipped potentially. There is seam splitting in several places throughout the book. Please see all photos.