1943 Local And Out-Of-Town Postage Rates (San Francisco, Ca)

The image below is a World War II Ration Book originally posted by Kehess in the Cover Calendar thread. As I think it deserves its own thread for discussion, I'm posting it here, too.

Can anyone explain why the 2-cent local (San Francisco) and 3-cent out-of-town postage rates are referenced on this document? Was it something unique to the OPA, such as a discounted postage arrangement with the post office for in-town mail? Was it due to the size of the mailer? Did it have something to do with World War II?



I have never heard of any instance in the mid-20th century of multiple postage rates depending on the location of where one mailed an item and I haven't been able to find anything on the internet about it either.

Although I know there used to be postage rates based on distance back in the 19th century, that was long before this sort of an item ever came into existence.

I'm curious if anyone has further information on the extra surcharge noted on this item.

Although I'm nowhere near as old as the cover shown, I'm surprised that I'm only now realizing that there was indeed a local delivery rate in effect on the date of the 1943 Ration Book shown.

In fact, the local delivery rate was in effect all the way back to 1933 and was abolished in 1944 as per these newspaper articles: