Printed matter surface rate was 1.5 cents from 4/1/1932 to 10/31/1953, for up to a 2 ounce item. Notice this has an unsealed side flap for inspection. The cover above is post WWII, by the use of the Zone number in the return address, first introduced in 1943.
A lot of years of collecting. Be organized. Look at every feature of a cover. Don't skimp on buying catalogs, monographs, and society memberships. I've heard is said that the library of a good collector takes up as much space as the collection itself.
In this case, the overall rate range from the Wawrukiewicz/Beecher U.S. International Postal Rates book, then narrowed down by the Zone 22 in the return address eliminating the pre-WWII possibility (Zone Numbers are a Zip Code forerunner, but a tangent for another thread), then narrowed down more by the Japan destination to after WWII. Additional research into the sending company and the recipient could narrow the use even more. To say 3rd class = printed matter = junk mail is a slight oversimplification, but essentially true, and a common explanation for low-rate foreign destination mail.
I still have a lot to learn and acquire. I do learn a lot from you and always appreciate your responses. You quite often blow my mind with what you dig up and the free knowledge you provide to all of us. Thank you!