Not sure what to make of this. I bought a batch of old postcards from the local flea market and a dozen or so of them had stamps. I think the stamp on this one is Scott #405 but why are there two cancel dates? One is 1915 and the other is Los Angeles 1913. I don't know much about stamps hope this isn't a stupid question.
You might take a look at Moe Luff's classic book, United States Postal Slogan Cancels. While this advertising slogan cancel was being used in 1912 in Los Angeles, other cities' Post Offices started in 1911! All of California was trying to get the word out for a long time!