Thought I'd share this one since it's pretty interesting. A few months ago I came across a video of what was claimed to be a Sentry Defender on YouTube. At first I was skeptical since it didn't sound like it was rotating and actually sounded a lot like an ambiance video. Later in the video you'll be able to make out some flashing lights. I thought were part of a separate visual warning apparatus of sorts. After looking at a couple of comments I figured out were it was. Turns out it was indeed a Defender and the first example of one ordered as an AC siren seen in the wild so far. It's a stationary installation setup in such a way that the compartment that would normally house the rotator is open with a set of beacons installed inside. I'm guessing the head is installed directly onto the top plate that covers the lights, where as in a normal installation the head is installed onto a turntable. It's pointed towards the lake, opposite of the camera, which explains why it sounded like ambiance in the video. Judging by the square cover for the motor I would assume it is a later model Defender. It's installed in Spring Valley Lake across the street from the local country club.
https://www.youtube.com/watch?v=tnsW4QZvKB0