This "short but informative film" (a la Mr Cholmondley Warner...) from British Pathé showing a series of ARP recruitment posters. I was surprised to see one that was new to me (the hourglass one, shown below). Some posters were designed but not released nationally and I assume this was one of them. Although the film appears to be dated 1936 I believe it was in 1939 that these were released.
Watch the film here
News about interesting insignia, ARP related info and period photos that turn up.