US Advertising Cover - 1939

My Monday Morning Mystery.

First of all, is this truly an advertisement? If so, was there a special rate for printed material - i.e. one and a half cents? And was a special postmark applied? There is a San Francisco machine cancel with slogan killer but it is not dated except for the rather confusing 1939(upside down 1 ???) at the bottom. Is this correct or is the date slug just missing or not registering?

I believe that back in that day there was the 1-1/2 cent rate for bulk mail, which is represented by the cover you show. (Remember, there was a 1-1/2 cent Martha Washington stamp in the Presidential Series of stamps in addition to the 1/2 cent Franklin stamps which appear on your cover. The entire reason that these denominations of stamps were made was to address that rate of postage.)

The fact that it was bulk rate mail is exactly why there is no date in the cancel. Typical for that class of service. Also typical that the piece would carry heavy advertising as a sales promotion.

The "1" in the San Francisco, California cancel is denoting the post office where the mail was sent from.

An exceptionally clear slogan cancel for the Golden Gate International Expo, though, which makes that cover a "keeper"!

P.S. Here's an example of a similar cancel with the 1-1/2 cent rate and no date from around the same time period (without the slogan cancel, of course):

Oh yes, it is a keeper. Thanks for the very clear explanation of the Postmark as well. I am continually fascinated by the history of these covers and have already looked up an article on the International Exposition as it was that slogan that first had me setting the cover aside to be looked at later.

Very nice, imaginative use of the cover's rear, and bright bold lettering!