Ceiling mounted devices, not smoke detectors

I have a device that I can’t identify. I’m sure someone can ID it in a heartbeat. There are no buttons to push. No screw holes. Those "eyes" are rigid. Cannot, remove it with a "twist". There is one of these on the ceiling inside the back door and one on the ceiling inside the front door. It does not have a door for batteries. It appears to be hard wired. It doesn’t look like the other smoke alarms.
W H Merritt

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