Hmm. Looks like an Erick Fire Siren. The shroud and the Mount looks almost identical to it. Otherwise, it could be a Siro-drone, due to the look of one louver being bigger than the other. Or even a Modified model 3, or 2, but this cannot be sure due to it not looking like it has been cut off completely. There would be a hole in the top louver.
Is this siren still around? If it is, try get some shots of it. It would help greatly.
A WW2 siren? In San Diego? That looks like a E57 yes, but it would most likely have been mounted on a pole that came with it.. Not on a telephone pole.
Conclusion
Okay so I think it is an Erick fire siren if it is, because it mentions about a “fire station” which is what Erick Fire Sirens were for.
If it isn’t, it’s probably one of Decot Engineering Work’s One-Made sirens. They are notorious for doing that.
I know little about their CD system but apparently they had “Fedelcodes” at one point.
This siren is long gone now, looking at the photo though it could just be a scream master as they came in a 2 shroud design as well. There are some other Scream Masters in the county known to have the same design.
The one below is an example, this was located at San Diego County Fire Station 44 before it got removed.
