I’ve been listening to episodes of the 1940s radio horror series Quiet Please. (Wonderful show, I’ve only just become aware of its existence). Episode #47 is entitled Thirteen and Eight: here’s the introductory paragraph of the summary.
Someone is jumping out of a window. A crowd of photographers is there trying to take pictures. A person gets in the way of the picture one of them is trying to take, and the photographer yells “13 and 8!” That’s the yell that they customarily use when someone tries to get in the way of a picture with the hope of getting to be in it if it’s in the paper the next day. This warning lets all the photographers around be on their guard.
Anything known on the phrase? The show apparently had a reputation for thoroughly researching backgrounds, so I’m assuming it’s a genuine phrase. (One of the best, and creepiest, episodes, for instance, The Thing on the Fourble Board, was accurate in technical details and lingo of the oil-drilling setting.)