On the back of the dust jacket this edition is called "The New Prize Guild Library" - The Worlds Best Books for Boys and Girls.
Moby-Dick is #17 in the series, which includes up to 37 Swift's Gulliver's Travels.
On the title page this is "Art-Type Edition" and "The World's Popular Classics"
The cloths and type style have a 30's feeling so I choose to mark it 1930's. Perhaps not. The lad on the right is wearing knickers (I wore them as a ski outfit in the 60's).
When referring to mens clothing, knickers is short for knickerbockers, while knickers in relation to women is something all together different.